Changing the sizing of the sections with sticky section on one side and multiple stacked sections on the other.

I would like to request a change to the coding for the split section plug-in, where you have a sticky section on one side and multiple sections on the other side.

The current code is set to split them 50/50, but I would like to set mine up to be 33% and 67% but currently, I can no sort out a way to do this. Thanks!