Had a 65 mm Viper HD but wasn't impressed with the higher magnifications. Now I run the little 11-33 x 50 and have been very impressed. I still need a bigger spotter when funds allow.... May pick up some 15x binos first to run off the tripod.
I am using a Vortex Razor HD 11-33x50, too.
This year I'm using a Vortex Razor HD 11-33 x 50
My Bride just surprised me with a Swaro STS 80 HD w/ a 20-60x eye piece for my birthday!!
Had to sell the swarovski 65mm, back to a minox md50 for a couple years. Float plane rides are more important than glass! The minox has proven quite good for the money.