I either have a couple of Jims kits or have built them for others and yes especially in drier climates, minor to severe cracking can occur. Between adding metal brackets in certain areas as you've mentioned fiberglass reinforcement also worked well.
I have a couple 3D printed kits, resin reinforcement worked well for me also. On another note it's hard to believe it's been 5 years since I built that kit. Glad to see it still helping the community. THT