The OSS website has a write up on this. From what I recall there has been a case of the clutch basket disintegrating under the stress. That is also on the website. The 750 clutch basket or the flywheel fouls #4 rod screw so one form an oiler has to be used for this combo of 750 tranny and cable clutch.
I have swapped 750 WC cases into my 1100 engine due to damage to the original 1100 cases. The 1100 transmission fit fine, so one assumes the converse is also true, as would apply in your case.
On a side note, the upper casing had to be trimmed to accept the larger 1100 cylinders though. along some of the inner edges. The drum, rods and all big end and needle bearings are housed identically in the cases. There are some things to be cautious of, in regards the bearings, they look similar but do have different part numbers. However in my case, I am running the 750 big end bearing on the 1100 shaft, in a 750 casing so that is a confirmed ok, can't say for the others.
Best of luck!
750W gearbox willl fit in 1100W cases . . . you just need to use the selector drum, selector gear shaft, and selector forks to match. You can modify the late series hollow 750W shafts for hydraulic operation. You cannot use the 750W clutch with the 1100W, because the basket fouls the crankshaft and conrods. The 1100W clutch can be used after some machining because of the shorter clutch shaft on the 750W. The 750W gearbox is much weaker (not surprising) than the 1100W's. Some racers made the swap to get the closer ratio's for the track, but really with the high/broad torque available on the 1100W's it is not an issue. My race engines pull hard from 6000 to 11500, and all I have conceded was to get a Robinson 2nd gear ratio to reduce the split between 1/2 and increase the 2/3 split for track work.
Streetbike . . . GSXR1100WS, Yoshi RS3 pipe, Factory Pro jet kit. Hillclimb car . . . 1298cc SBM big block, Yoshi stage 2 cams, FCR41's, Dyna 2000, MTC lockup clutch, Geartronics paddle shifter. Circuit race car . . . currently 1145cc JE kit, but building 1118cc Wiseco Gixxer with Hahn Racecraft EFI turbo.