As I started to fit cabin frame into brackets, I realized I somehow had ended up 3/8" too narrow across the width of the fuselage. I could stretch the frame to fit by using clamps, but I was afraid the warping would be enough to cause problems with fitting the canopy. After pondering solutions for several hours and checking the builders' message boards (which indicated this was a common issue, though mine was more severe), I decided to go with disassembling the frame, cutting the narrow strips that run the length of the frame, and increasing the separation between the left and right halves. To secure the halves, I made new stiffener plates for the fore and aft faces, and doubler strips that I spliced onto the original strips. Lots of work and I still have the bulk of the blind riveting to reaccomplish, but it fits perfectly now!
