Re: Question on the Vortex Viper PST
Yes, a 40 MOA base is way too much for that scope. As much as I really like this scope, one of its limitations is travel. If you're doing a bunch of shooting over a mile I'd recommend spending a bit more on a NF or SS 5-20 HD.
The distorted view, as mentioned, is a function of the way the scope is designed. Lots of more expensive scopes will exhibit this as well.
Keep in mind it is only a problem on the low powers. It completely goes away around 8X-10X, so if you want to run around with the scope on 6X at your 100 yd zero with a 20 MOA base, it does pose a real problem as it also seems to make the eye relief a bit funky. But if what you mainly use the scope for is shooting long range on the higher powers, you should never notice it so it shouldn't be a problem.