Sorry about the delay.. I haven't been logged in for a while.
In the end, I got a tank from an A model (same as the B - Tengai, except the A tank doesn't have the tabs on top for the fairing). Thats a bunch bigger than the C model.
There are only a few probs with the C model, and most can be fixed:
1) small tank - put the tank from an A model on it (seat will need to be bodged to fit, and C engine bars will no longer fit).
2) skinny rear subframe, and associated puny rear luggage capacity.. you can weld up a supporting bar onto the rear subframe, or just try to minimise the weight!
3) less availability for after-market stuff.. most of the stuff comes from the US, and it's all A models over there. I've kitted my C out successfully, but it's required some minor alterations (for the new engine guard, for instance) to make it work, and the engine bars in particular were hard to come by (mine no longer fit, so they might be up for sale).
4) Lack of screen - aftermarket givi screen for £10 on ebay!
Hopefully this doesn't come too late for you..