This bit is well annoying! I've gone to fit the rs1-3 section and realised the "open" end of the assembly has ended up nearly 10mm over the 421mm it should be from inside wall to inside wall
The bottom end measures up fine and the corners are 90 degrees as they should be so I guess the metal has warped at bit on me during tack welding? Should I 1) just put it on as is and adjust the measurement from the center line, 2) try and knock it with a hammer into the right size, 3) chuck it in the scrap pile and try again?