Everything you've mentioned is what makes sense to me. The more centered and the narrower the pattern the better, but I don't think that is THE most important aspect. We arent working on chevies here, so I think pushrod length issue is overblown (except Magnum guys), as long as yours are the "right length" you're fine.

The 90 degree at midlift makes sense to me as that should result in the narrowest sweep pattern. But I've also been advised to have the roller on the valve tip only move in "one direction." IE the roller moves across the valve tip towards the exhaust side when opening, and rolls back to the inside when closing the valve Having the rocker shaft "too low" will achieve that.

I'm using spacers on my Trick Flow 240 heads with solid roller cam. Rocker shaft has been raised and moved away from the valves. My "ideal geometry" would have the valve reach 90 degrees before mid lift. That would do two things, ignoring lobe profile: the valve would be opening the quickest at lower lifts and slowest near peak lift. #2 it would conform more to the roller moving in one direction advice I've been given Easier said than done.

Ultimately, I took the easy road. Used the "recommended" parts and talked to someone smarter than me. Mike @ B3 Racing Engines