Well if you really wanna know then call Vince and ask. I chatted with him a couple hours a decade ago. He'll probably tell you that the 230 isn't such a great engine to build unless you have him install a new rod and weld the crank. He can put the 17mm rod on and it doesn't cost that much if you're willing to split the cases. Yeah a 230ES would be pretty cool. A lot of the reason I don't want to fiddle with mine anymore is I don't feel like kicking it incessantly. I didn't think of filing the cam but yeah you could file off the round part to increase the lift then file off the peak of the lobe to lower the lift and increase duration. I've heard of guys doing that before. It doesn't even matter if the round part is polished since the rocker just glides over it. But if you file the lobe you'll have to assemble it and use paint to determine if the cam contacts the rocker fully.