which is better for High rpms? to what I understand X beam (pauter) has less windage loss which makes lubrication easier at high rpm, its also very strong on the compression stroke but weaker on the intake stroke.

I dont know much about the other designs.

 

up

 

I beam is generally regarded as the "best" design, for a couple of reasons.

An H beam rod's oil passage way to the piston pin is limited in size due to the single central rib.

The proximity of the bolt holes to the double rib on the rod cap concentrates stress on that area and makes it weaker.

Generally an I beam rod such as an Oliver can be made lighter due to better design and use of metal.