i seen the futaba 3pk comes with the r603fs rx, will it work with the r603ff rx's?? Wanting to upgrade my tx, all my receivers are the ff's, i looked it up on futaba's website and on the chart it looks as if they are the same(the fs has 1 external and 1 internal wire as the ff only has the 1 external wire) but it shows the fs with the module though. Wanna make sure before I buy one, thanks for the help.

Yes...works just fine. I have the FS in one of my cars and the FF in another, both bound to my 3PKS.

You just won't get the diversity antenna benefits with the FF, as you pointed out, but it most likely won't be noticeable anyways.