Hey Andrew,
Tapping and putting in a new screw would seem like it would work fine. On my reed set up i went with Boyesen FiberGlass reeds opposed to the carbon fiber reed set up. They seem to work we'll and have no wear that I can see after a year of racing and I installed them last year around Feburary. If i remember correctly those screws are a certain length, so be careful when buying new ones after you tap and as bruce says use blue loctite when putting them back in. If you are going to go the aftermarket, the boyesen rad valve didn't affect my friends 02 Cr250. He has the same jetting as me and left every thing the same. I personally didn't notice a difference with rad valve on.
Erik