Hi LMX,
Doubt its the swingarm alignment. I think you will find the the F4/F5 has a 145mm spaced rear swing arm. This then fits the 10mm floating brake (on the left) and your 135mm rear hub over the 12mm axle? So given the wider swingarm than a standard 135mm rear axle bike the chumba allows the rear rim to be more central over the hub (most bikes need to pull their rim to the cassette (right) side to have them siting in the midle of the frame (and this in turn makes for a weaker wheel).
Hence when you put you current wheel in the F5 its offset or out of dish to the right hand side (cassette side). Depending on how long you spokes (and thier threads) are the wheel should be able to be "pulled" (by a wheelbuilder) to centre in the swingarm.
Enjoy, relax and smile you have got your self a great bike.
Cheers.:thumbsup: