There's a line in the
BRB about mounting models that do not have bases on them, and to use "similarly sized models" as a guide. Attack bikes fit swimmingly onto 60mm bases, and are too large for 40mm bases.
TL;DR dreadnought sized bases are great and there is a rules basis to mount your guys that don't require them.
If you run into someone claiming
MFA, just ignore him because that's pedantic. It's actually a detriment gameplay-wise to mount an attack bike because it increases the area it can be charged. Not much of one and not enough to warrant not doing it for the purpose of having a cooler looking model, but it's worth noting.
As for the
RW bikes, converting the
TW-boltguns into the
RW Command fronts is really hard and a pain. I highly recommend NOT doing that, and just using the winged fronts found
on this sprue. You get 3 of them I think with the Ravenwing Battleforce Box which is still the best dollar-for-dollar way to build up a biker force
at MSRP. 6 bikers + an attack bike is already the cost of the box and you get a land speeder with 3 ravenwing upgrade sprues on top of it.