Apparently the F2 head can be identified by having different drain back holes to the earlier heads -
Head Drain-Back Hole: The F2 head has a common head drain-back hole, unlike earlier models, which eliminated the middle drain-back holes.
I have to confess that I'm not quite sure exactly what I'm looking at, but I'm sure I'll be finding out very shortly.
Yes, correct. They were struggling with development (without big changes) on this last iteration. The objective looked to keep more oil at that level by restricting drain volume is my view of it.
The bigger valves were moved further back upward into the combustion chamber to give clearance at their head diameter, both between them and bore periphery naturally.
The angle between them often quoted as changing by some sconces, incorrectly as for example I've worked with.
But it did put the top of valve stem higher in relation to the arc of movement in tappet face, which ultimately put more side load on the valves from that arc of interaction geometry. It's primarily this that affects wear on valve guide, exhaust predominantly.
The F2 has to use higher dome piston to maintain compression in that bigger chamber too. Valve springs stepped up in rating, higher rpm ceiling etc.
Also std F2 has an oil "cooler" plate fitted between filter housing and crankcase, extra fins etc and longer filter bolt to accommodate (I think) but worth checking.
Mounting F2 head on F1 or K bottom you'd have to consider and check oil return path etc. Or the opposite swap likewise.