you want a little girdle with your notches?

 

you can run d15 rods and push that piston up a few mm It'll give you better rod ratio too. Don't worry about that gridle. When everything in torqued down they just work like normal main caps. I would just completely cut off the pieces you are grinding. It will have plenty of lateral support from the center oil passage. Final result would like 5 normal main caps w/ the oil bar across it.