Keep in mind that model F's have individual barrels in a metal plate, so they're easier to change the layouts, etc. in. IN a model M, you're stuck with cutting the barrel plate to size and keeping the keyspacing. just something to consider. Still, model F PCB's operate on black magic, so maybe it's best to go with the M on this one (but putting M guts and F barres together can be the best, perhaps.