The stiffest feeling frames laterally have either had super beefy chainstays such as a Tesch S-22 1.125" at the bottom bracket, and squashed where the tire and chainring (42t) would pass, and the Masi 3V with the 25mm chainstays, slightly oval for the same reasons behind the socket.
One could in a fillet brazed mode, tilt the oval stays to possibly help IF you don't get yourself in clearance trouble. The original diagrams are exaggerated I think. I would try the lower right diagram so modified.