They do have oil rail support. And explain why it is not good to have the top ring that close?
It is better for endurance to keep the top ring further from the heat at the very top of the piston. That heat is tough on the top ring and can cause it to distort and lose seal, and the pin can also suffer by being so close.
A little less stroke may take you away from that 434, but will let you use a shorter rod and off the shelf pistons with better ring spacing. 3.8, 3.85, and,3.875 will still get you 420+. Then you can support the oil rail but get the top ring and pin down.