Wrong size of underbraces

[RarrugasTetra]

Dear Developers,
I have a problem with underbraces in my formulas; they are too small. Here is an example:

require 'mathematical'

var = Mathematical.new.render('$$\Phi = \underbrace{\sum_{i} \gamma_i \left( s_i M^{model}(s_i) - s_i M^{exp}(s_i) \right)}_{\Phi_{GED}} + \alpha \cdot \underbrace{ \sum_{j} \gamma_j \left( p_j^{model} - p_j^{QC} \right)}_{\Phi_{QC}} \rightarrow min$$')

File.open("test.svg", 'w'){|f| f.puts var[:data]}

You can run it and check the test.svg or you can see it here

How to fix this?

Thank you.

[RarrugasTetra]

Is there any chance to fix the problem?

[4e554c4c]

closing in favor of higher-quality issues #111