I did think of going the two aileron route. This has drawbacks. Twice the servo current which gives shorter flight sessions and increases the roll inertia so I stayed with what I found to be the most solid dependable method I could adopt and that was not far from the original. I did add some clevises for assembly adjustment at the bellcrank end and I did add a 90degree kink to the servo for security. It turns out I can get the hole to be altered quite easily if I want to adjust the throw at the servo end although I think it will not be needed. There is only one rod from end to end to eliminate any slop which is the last think I want. There is a geared down drive to the servo by the use of different lengths of the bellcrank.
I am not sure what the amount of throw should be but I am certain that no differential was used on the original. Mine had just enough so that if there was any chance of the lower aileron being more than the upper one this should eliminate it.
I have today been trying to fit the steering linkage. Good fun (it isnt). However I am getting there slowly. A smaller battery pack may help. I ordered one today (800maH) and the fuel tank looks like the Kavan Flexi tank will be the one to use. We will see.