Monte,

I agree with your analysis of the how the crank moves, however I dis agree with the not using a girdle. you don't want your caps to bounce as that adds a lot more stress to the webs as the stud threads are always pulling at the main webs and they act like an impact hammer. the girdle is there to help clamp down the caps so the caps are not solely relying on the main studs to hold them down.

since different caps are experiencings forces at different times in the rotation of the engine it makes sends to tie the caps together and to the oil pan rail of the block so the loads are more distributed. will it be even? nope. but adding and distrusting stresses and load to areas of the block that aren't being used, like the oil pan rail. will take some of the load away from the main webs.

will adding a girdle never fail a block? nope, but it will give it the best chance to survive more abuse.