Ok, recompiled with 1.6.7, and beta Teensy, still exact same issue. Stuck with that 250x250x250mmH square.
Interestingly, this hex is a good deal larger than the last I compiled.

What the heck am I missing here? Is there a size sanity check code? I'm going to try a different source now, but I was getting issues with the Y endstop pin assignment before. The Y endstop would not trigger under any of the newest versions, didn't even get around to checking other mechanical properties, as that was a big no go to begin with.