Hi, The four 1928 TT bikes that I have owned (still have one), had rather agricultural, very long footrest hangers that bolted onto the usual two bolt holes to the rear of the flat section on the bottom frame rails, putting the actual footrest about inline with the gearbox layshaft. The 1929 TT bike that I am just finishing has a much nicer and lighter arrangement, with much shorter hangers that bolt on using the same hollow bolt that also secures the rear of the gearbox tray. This again puts the footrest about in line with the gearbox layshaft. Both types of course prevent the provision of a kickstart, so they are ‘run-and-bump’ machines only. This arrangement means that the TT machines also have rearset brake pedals too, pivotting in a lug on the frame that is on the lower frame-stay section of the frame. As of course all these machines are hand gearchange there is nothing for the rider’s left foot to do, but if you want a R/H footchange you will have to rig up both a L/H rearset brake pedal, and a R/H rearset gear lever, not easily done….
If I were you I would have a close look at the ex-John Hartshorne machine, now owned by Martin Heckscher, to give you some ideas. Also look in the book called “The First Scott Scene”, as there are some racers in there with different arrangements.
It’s your bike, but I would urge you NOT to mutilate any original Scott components in this exercise !