true, but the math I used is possible to use other offsets.
also it occurred to me that growth needs to be, I think, < 0.5 since a single wall thickness would collapse with offset 0.5, maybe better to use 0.4, in which case, if you still want approximately 1.5, that would NOT be integral.  Better to use steps and the critical step-size to determine the margin.  than try and derive the step count from margin/step-size.