There is a standalone patch in FEBuilder for non-SkillSys fixed growths
Patch Name:FixedGrowthsMode @FE8U
Author / Source:TR143 [FE6,FE7,FE8] Fixed Growths Mode
Now, having not used it myself I can’t 100% vouch for whether it works, but assuming it does what it says, making a fixed growths version should be as simple as installing this patch.