Triangulation my friend...
Stiff is great but too stiff is really bad. Every great frame has flex intentionally built in for the type of suspension, use case and rider preference. Gotta give somewhere...might as well make it intentional.
I’ll take some pictures of the two frames I’ve done in Solidworks once I’m at the shop tomorrow. One is for AHRMA USCRA GP200 and the other is for a BMW R100 motor.
I’m also building up my Derbi Variant for NEMA since I’ve been bored and wanted to play with a moped again.