Jolly, I just checked Tower & the weights are all pretty close. OS .46AX W/Muffler = 17.2oz, Tower .46Pro W/Muffler = 16.9oz, & the TT Pro .46 W/Muffler = 17.01oz W/Muffler so they are all 3 right there in that 17 oz range with a .3 oz difference between the heaviest & the lightest. Personally I wonder if the TT isn't the best bang for your buck among the three. I don't own one but have many friends that do & have been nothing but impressed with the smoothness of the way they idle & run as well as having good power too! They seem to hold an idle longer than my OS's without loading up too. All around a good high quality strong running engine from what I've observed. Just my personal opinion though.
Just food for thought a friend bought the new OS .55 & hung it on the front of his WM Dego Red & it's really scoots along well. Seems like a really nice engine!!
http://www2.towerhobbies.com/cgi-bin...?&I=LXNMD1&P=0
If the extra $40 doesn't bother you, it might be worth looking into.