I like the schn. 90/8 SA and schn. 210/5.6 Symmar-S, the schn 150/265 convertible, and the nikkor 300/9 M. Several of those are really not up to provide the full circle, but it usually doesn't bother me. If I go nutty enough on the movements to warrant it, I put on the nikkor 150 SW (although that is really overkill and it usually stays affixed to my 11x14). The longest lens I've used on it so far was my apo nikkor 360.
I have the Shen 4x10 too, in fact I got it from the Keith above, if I remember correctly! Shen made me a 5x8 back for it for something like $250 and I got the film holders from chamonix. Shen makes 5x7 and 5x8 backs for that camera. They'd probably make you any back for it if you asked nicely.