Bot Size

The bot is 36x36 and doesn't rotate, always axis-aligned. The 50.91 sounds right (and I remember 25.xx as the max half width). Last point of note is that each tick, bullets advance, then Robocode checks for collisions, then bots move.

Not sure about the 16 - I'd guess some Minibot-ism at play.

Yeah at a perfect 45 degree angle from the AABB, it would have a width of <math>18\sqrt{2}</math>.

Ok great, cheers! Using 18 for checking distance to wall and ~26 for checking overlap of things like wave bullets etc! :)