Ummm approach angle on my modified GX Head was 22 degrees but that is a number that has just popped into my head. I don't recall the angle of the other oval port heads off the top of my head but I think they are around that mark maybe more like 17-20 degrees.

I'm pretty sure the designs you were thinking of did have the join, think it was for a turbo setup,not sure.

I have a few old round port heads somewhere all dirty and crap. You can have one for free if you want it.