Xerxes, the thoughts that are conveyed in Tex Smith's Flatty book, seem to point to the intake breathing being affected more by making the transition area smaller, than the exhausts expelling of gases would be, in a true Flathead. I am not as familiar with an F-head configuration as I would like to be, but from pics I have seen of a cylinder head, it appears to have it own separate channel or pocket to carry the charge gases in. So it probably would not be as sensitive to cutting or milling the head surface as a conventional Flatty engine would be. If that is the same style head as the Edgy design, maybe he could be contacted to add his thoughts to this subject matter, then we all could benefit from his knowledge and expertise. I would hate to assume this to be the case with this engine, and it turn out to not be accurate info for you. But that is my off the cuff thoughts just from seeing pictures of the F-head/block configuration. Oops, forgot to finish the rest of your questions. If you did cut the head a lot to get more compression, you can always relieve the block, just in the area where the exhaust passes thru the transition part. Since it is a much narrower passage than that of a true Flatty, it might not compromise or take away from much compression you added by cutting the head to start with. Also, tapering or trimming away at the valve guides is going to improve flow also, so I would recommend doing that. If the guides are removable, or replacable, you can taper them in a lathe before you install them, that way you can keep the amount you remove from them more consistent. Hope this helps out....
