How tall are you? And are you looking for 2009 or prior year Thruxton?
For example, I ride Bonnie (07) with Thrux Gel seat, which is taller than normal, although I'm only 5'4". I ride hours straight without no pain at all.
My friend is 5'7" and riding clip handle Thruxton, and I must say, he looks all stretched out when I see him riding. I hopped on 09 Thrux with bar handles and I felt quite comfortable so 09/-08 will make huge difference on Thrux.
On the other hand, another friend of mine is 6'2" and he is getting the foot pegs altered to have more leg room.
Probably stating your height, inseam and Thrux year would get you better info.