I thought the center 3 main caps were the most loaded, that's why they're always the ones with cross-bolts or extra splayed bolts? And thrust loading is totally separate from radial loading with much lower forces unless you're dumping the clutch doing holeshots in a stick-shift car. IIRC the momentum of a piston/rod assembly at 5000 RPM is on the order of several tons of pressure pushing on the rod journal back-and-forth hundreds of times a second.
