If you use the F frame, the welded on features allow use of the F model brake lever, foot peg, and kick lever, which all clear and work as they should.
Imo, the F header on a K bike is a match made in the painful style. Better to find a K frame.
I totally understand the desire. I think the stock Honda header is the best looking 4 into 1 on the planet. But, each and every adaptation to the K frame I've seen looked kludgy (and often works poorly) at best.
Save yourself major headache and get a header designed to fit a K model, is my recommendation. Further, mufflers won't be much issue, either.
Cheers,