My xy is off slightly (1/8″ over 24″) when the xy is at rest (motors off). The frame is square though. I created a spacer that I use (4 of them, 2 for x and 2 for y) to square the xy before I print, or more precisely, just before I engage the motors. Once the motors are engaged all is good.
This one is for 25.4mm tubing, so “J” build.
Can’t post the stl but this is what it looks like.