When results with units are passed to IPluginLowLevelEvaluationFast, further actions looks silly if passed units aren't preprocessed;
1) using a custom unit for the result, MathRegion adds a correct but useless unit correction (it is equal to 1);
2) using result for further operations is not possible "Units don't match" error;
Workaround (plugin-side); use SMath.Math.Decision.SymbolicCalculation(result.ToEntry(), new SMath.Math.Store());
i.e. result is ok if passed as value*'kg/'m/'s^2 but fails if passed as value*'Pa