Hi P95,
Sorry your double-D's aren't working out for you. I have a question though. When you have the glasses on and are looking straight forward into a mirror, do your irises fall in the middle (non-magnified) portion of the lens, or does the top bifocal cover some of the iris? If it's the later, then they may not have fitted you proper.
My double D's look the exact opposite of yours, with a full bifocal in the lower lens and partial in the upper. Looking straight forward my irises fall right smack in the middle of the two bifocals which allows for normal vision. I have to tuck my chin slightly to use the upper bifocal when shooting.
Rudy Project makes a model called the Exception that has a flip up sunglass feature to be used with prescription inserts. Basically what you end up with is two thick layers of Polycarbonate protection instead of the usual single layer.
http://www.rudyprojectusa.com/intros/
I recently purchased a pair and had two sets of prescription Polycarbonate inserts made up. One set has my reading prescription bifocal in the lower portion and the other set with a bifocal in the upper lens that is powered to allow exact distance focus from my eye to the the front sight.
I've found out that for use when shooting, changing out "only" the lens that covers my master eye with the upper bifocal, while leaving the other, lower bifocaled lens in place, allows for a more natural sight picture. The right eye is able to focus on the front sight like it should and the left does what it is supposed to do without the magnification downrange.
TK