KH36 frames and Qx36 frames are the correct width for a schlumpf hub. The Qx frame will likely need filing around the bearing housing though. Both these frames are incompatible with the FS hub without some modification.
The big problem that you are going to run into is the bearing size for the FS. Both the frames use 42mm bearing housings. The schlumpf hub works by using one of the bearing housings to lock the hub to the frame providing a fixed sun wheel with the axle attached to the planet carrier. By using bearing spacers, you would make an unmodified hub very dangerous to ride as the sun wheel would be able to spontaneously slip creating a freewheel.
Rumour has it that new 125mm and 100mm spaced schlumpf hubs should soon be arriving that will negate many of the problems we have with the current generation.
I have been riding for a number of years on a MUNI 24 and and a 29er. I also cycle tour (2 wheels) and want to try and do some much longer rides on a 36 inch unicycle, best of both worlds.