Yes if you are going to use a one piece base then you need a longer base designed for the true magnum length actions like the H&H.

Personally I like the two piece base over the one piece base. I don't like the "bridge" over the receiver being in the way and I prefer to have 4 screws holding the scope on rather than just three.

On a STW I would have a 3-12 or a 4-12. Not sure how much money you want to spend on optics but my choice would be a Burris signature select in 3-12X44 if you got the money for it.