diff --git a/pmd_beamphysics/wavefront.py b/pmd_beamphysics/wavefront.py
index 100828b..0a1c846 100644
--- a/pmd_beamphysics/wavefront.py
+++ b/pmd_beamphysics/wavefront.py
@@ -8,6 +8,7 @@
 import pathlib
 from typing import Any, List, Optional, Sequence, Tuple, Union
 
+import h5py
 import matplotlib
 import matplotlib.axes
 import matplotlib.pyplot as plt
@@ -232,20 +233,7 @@ def is_odd(value: int) -> bool:
     return value % 2 == 1
 
 
-def _fix_fft_dimension(dim: int):
-    """Get a dimension that's efficient for the FFT - and also odd for symmetry."""
-    while True:
-        next_dim = scipy.fft.next_fast_len(dim, real=False)
-        if next_dim is None:
-            raise ValueError(f"Unable to get the next valid dimension for: {dim}")
-        dim = next_dim
-        if is_odd(dim):
-            break
-        dim += 1
-    return dim
-
-
-def _fix_grid_padding(grid: int, pad: int) -> Tuple[int, int]:
+def _fix_grid_padding(grid: int, pad: int) -> int:
     """
     Fix gridding and padding values for symmetry and FFT efficiency.
 
@@ -260,29 +248,29 @@ def _fix_grid_padding(grid: int, pad: int) -> Tuple[int, int]:
 
     Returns
     -------
-    int
-        Adjusted data gridding.
     int
         Adjusted data padding.
     """
-    # Grid must be odd for us:
-    if not is_odd(grid):
-        grid += 1
 
-    # Ensure that our FFT dimension is odd and optimal for scipy's FFT:
-    dim = _fix_fft_dimension(grid + 2 * pad)
-    assert is_odd(dim), "FFT dimension not odd?"
+    def is_good(dim: int) -> bool:
+        return is_odd(dim) and scipy.fft.next_fast_len(dim, real=False) == dim
+
+    while not is_good(grid + pad):
+        dim = scipy.fft.next_fast_len(grid + pad + 1, real=False)
+        if dim is None:
+            raise ValueError(
+                f"Unable to get the next valid FFT length for: {grid=} {pad=}"
+            )
 
-    # Fix padding based on our optimal dimension:
-    pad = (dim - grid) // 2
-    assert not is_odd(dim - grid), "End dimension not even as expected?"
-    return grid, pad
+        pad = dim - grid
+
+    return pad
 
 
 def fix_padding(
     grid: Sequence[int],
     pad: Sequence[int],
-) -> Tuple[Tuple[int, ...], Tuple[int, ...]]:
+) -> Tuple[int, ...]:
     """
     Fix gridding and padding values for symmetry and FFT efficiency.
 
@@ -297,8 +285,6 @@ def fix_padding(
 
     Returns
     -------
-    tuple of ints
-        Adjusted data gridding.
     tuple of ints
         Adjusted data padding.
     """
@@ -308,21 +294,20 @@ def fix_padding(
             f"Got: {len(grid)} and {len(pad)}"
         )
 
-    result = [[], []]
+    final_padding = []
     for dim, (dim_grid, dim_pad) in enumerate(zip(grid, pad)):
-        new_grid, new_pad = _fix_grid_padding(dim_grid, dim_pad)
-        logger.debug(
-            "Grid[%d] %d -> %d pad %d -> %d",
-            dim,
-            dim_grid,
-            new_grid,
-            dim_pad,
-            new_pad,
-        )
-        result[0].append(new_grid)
-        result[1].append(new_pad)
+        new_pad = _fix_grid_padding(dim_grid, dim_pad)
+        if new_pad != dim_pad:
+            logger.debug(
+                "Grid[dim=%d] grid=%d pad=%d -> adjusted padding=%d",
+                dim,
+                dim_grid,
+                dim_pad,
+                new_pad,
+            )
+        final_padding.append(new_pad)
 
-    return tuple(result[0]), tuple(result[1])
+    return tuple(final_padding)
 
 
 def get_shifts(
@@ -584,8 +569,7 @@ def fix(self) -> WavefrontPadding:
 
         Such that the total array size will be: `grid + 2 * pad`.
         """
-        grid, pad = fix_padding(self.grid, self.pad)
-        return WavefrontPadding(grid, pad)
+        return WavefrontPadding(self.grid, fix_padding(self.grid, self.pad))
 
     def get_padded_shape(self, field_rspace: np.ndarray) -> Tuple[int, ...]:
         """Get the padded shape given a 3D field rspace array."""
@@ -593,10 +577,10 @@ def get_padded_shape(self, field_rspace: np.ndarray) -> Tuple[int, ...]:
         if field_rspace.ndim != nd:
             raise ValueError(f"`field_rspace` is not an {nd}D array")
 
-        if not all(is_odd(dim) for dim in field_rspace.shape):
-            raise ValueError(
-                f"`field_rspace` dimensions are not all odd numbers: {field_rspace.shape}"
-            )
+        # if not all(is_odd(dim) for dim in field_rspace.shape):
+        #     raise ValueError(
+        #         f"`field_rspace` dimensions are not all odd numbers: {field_rspace.shape}"
+        #     )
 
         return tuple(dim + 2 * pad for dim, pad in zip(field_rspace.shape, self.pad))
 
@@ -636,6 +620,12 @@ def __init__(
     ) -> None:
         if not pad:
             pad = (40,) + (100,) * (field_rspace.ndim - 1)
+
+        if len(ranges) != field_rspace.ndim:
+            raise ValueError(
+                "'ranges' must have the same number of dimensions as `field_rspace`; "
+                "each should describe the cartesian range of the corresponding axis."
+            )
         self._phasors = None
         self._field_rspace = field_rspace
         self._field_rspace_shape = field_rspace.shape
@@ -1003,7 +993,13 @@ def plot(
 
         sum_axis = {
             # TODO: when standardized, this will be xyz instead of txy
-            "xy": 0,
+            # "xy": 0,
+            # (1, 2): 0,
+            "xy": 2,
+            (0, 1): 2,
+            "xz": 1,
+            (0, 2): 1,
+            "yz": 0,
             (1, 2): 0,
         }[plane]
 
@@ -1055,3 +1051,25 @@ def plot(dat, title: str):
                 fig.savefig(save)
 
         return fig, axs
+
+    @classmethod
+    def from_genesis4(
+        cls, h5: Union[h5py.File, pathlib.Path, str], pad: int = 100
+    ) -> Wavefront:
+        from genesis.version4 import FieldFile
+
+        field = FieldFile.from_file(h5)
+
+        _nx, _ny, nz = field.dfl.shape
+        z_low = field.param.refposition
+        z_high = z_low + field.param.slicespacing * nz  # TODO: off by one?
+        return cls(
+            field_rspace=field.dfl,
+            wavelength=field.param.wavelength,
+            ranges=[
+                (-field.param.gridsize, field.param.gridsize),
+                (-field.param.gridsize, field.param.gridsize),
+                (z_low, z_high),
+            ],
+            pad=(pad, pad, pad),
+        )