so interestingly enough, can’t seem to find 3/8" mdf or birch here for the frame…
questions then:
what material did you use and where did you get it?
and can I use 1/4" or should I use 1/2" mdf if I can’t find 3/8"? - I don’t think it should matter too much with respect to strength, but not sure if the extra space given for 3/8" material will make it sloppy with 1/4" material…
I found a local store that sells this kind of stuff. The HD and Lowes probably won’t. Searching “lumber” into google maps has worked well for me (in Denver). BB isn’t cheap though, I think the 60"x60" 3/8" was between $40-$50.
1/4" Is fine, I think the weakest places will be the corners (which the Heffe plate will fix) and the upper corners of the XZ frame, which are probably fine, and I just get paranoid. IIRC, Ryan’s are all 1/4".