Preform should show guides for build volume minus required support size

I print many objects that are close to the limit of the build volume in some dimension. Often, I orient an object, generate supports for it, only to find that the supports move the object outside of the build area. Perhaps Preform could show a dashed line around the build volume minus that required for supports in X/Y/Z? This seems like it would be simple to do, and it would let me dispense with the trial-and-error of orienting, generating supports, adjusting slightly, re-generating supports, etc.

So, is the footprint of the base always the same amount larger than the footprint of the actual print, and if so, what is the distance of said offset? I suspect this could be found by the end user with simple tests using basic geometric shapes, resulting in a rule-of-thumb that goes like “keep your actual prints within 1/3 of a grid square from the edge in PreForm”.

It won’t know if supports extend outside of the build volume until it generates them