Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
The closest part to the tyre is the torsion bar. With a 120 tyre, it only leaves you about 10mm
4.10 on the front is tight but, it depends on the mudguard. You will also get a lot of tyre flex at that size on the front. Most people drop the wheel rim size to 18" on the front because there is a greater range of that tyre size
The TT100 sizes you quote are what we fitted when the bike was current
Zero