Percent of lost lift due to 58 degree lifter angle?

Agree.
I have 1.5 Harland Sharp rockers and a smallish cam for what I have.
I asked Dwayne if it was worthwhile to put 1.6 rockers on, and he said unlikely to be worth doing, so I didn’t.
Yeah and a handful of tests out there support this also. It's a bit counterintuitive but at least in some cases the extra lift doesn't do anything at all.

Everybody's favorite dude Richard holdener did a 5.3 test with a BTR cam one was rated for stock springs and the other one higher lift and required spring upgrade. Otherwise basically the same cam timing events. Guess what....Just about zero....nada.... difference between the two in terms of power output.