I mentioned the SWFA because the OP is already going with a Douglas 5A barrel. The rifle is going to be heavy anyway, it might as well be balanced, and have a scope capable at longer ranges in order to take advantage of the weight.
One of the worst rifle building mistakes is to build a 'tweener, IMO. For instance, a 10 lb. rifle which has a scope that can't be dialed (or has poor adjustment repeatability). Not all that great for longer range, yet not very portable. A 20 caliber 5A contour at 24" isn't going to turn out a light rifle even with a light stock and scope, so might as well take advantage of it's positive qualities.
If it was being built fairly light as many of us suggested, a lighter scope would be just right.
I'm right there with you on the extra weight being unnecessary in a calling rig. I started out years ago with a heavy rifle for calling, and have steadily gravitated towards lighter rifles, finding a happy medium of steadiness to portability around 8ish lbs.
