I fit TT100's to all of my older bikes as tyres become due for change. On the 500/4 I use a 4.10 front and rear (as we did in the 1970's) and on the 750 a 4.10 front and 4.25 rear. Central tyre usually hold them in stock.
If you want to see pictures of them fitted, send me a p.m. with your e-mail address attached and I will forward a couple to you. (There are some on this site already, although I am not sure where, that were kindly posted by another member for me as I cannot seem to upload them myself).