I tried several things like that but not making a new bolt. I'll let you try that one!
IMO the stock design is perfectly adequate if you observe factory redline. The rockers simply do not need as much oil flow as the rod and main bearings do.
Possibly more flow is needed for continuous operation over 5000 rpm, but I'm dubious even about that. And if so, I'd be looking at roller rockers anyway. The only reason to need a continuous oil flow is to carry away heat.
IMO, dirty oil is much more of a problem than lack of flow.
I've lost track of just when I had a pair of rocker shafts rebuilt last, but it was some time before 2000. The 2nd one is still on the shelf, as the first one is still in good shape with probably over 100,000 miles on it. (I moved it from the wreck.)