Oh man, very cool. It's a wonder what you can find on this message board if you actually spend the time looking around a bit eh!
So it looks to me that the TM 4.3 has a rail under the barrel, where as the 5.1 doesn't. This makes me think that if a guy wanted to put a red dot style scope on top of the thing, the 4.3 would be far easier to do this on than the 5.1. I am sure that it could be done on a 5.1 but it looks like a lot more work, right?
Great responses boys, I am learning a lot today!
Thanks
Gord