Thanks Fotoman.
I had reservations about the 90XL, excellent lense though it is, because its useful circle of coverage is too close, (so I felt), to the size of the film.
Hence today I ordered the 6x24 with the 110XL.
Its a pity that the spacer/cone/focus mount etc are not sold separately from the camera body, because I had thought of keeping the 150XL permanently fixed to this and swap lenses without having to recalibrate every time.
Any news of the bellows attachments yet?