Stupid question, but are you actually sitting on the saddle in such a way that you're letting it take a good amount of your weight? I only ask because I had a similar problem, and had had a couple of fits which hadn't addressed it; it was only when I realised that out on the road, with winds and trying to ride efficiently (as opposed to on the jig), I was pulling down into the bars and rolling miles forward on the saddle. With a slightly longer and lower stem, and actually making sure I used the saddle to take some weight, the hand discomfort went away, and I got much better glute engagement to boot.
Stupid question, but are you actually sitting on the saddle in such a way that you're letting it take a good amount of your weight? I only ask because I had a similar problem, and had had a couple of fits which hadn't addressed it; it was only when I realised that out on the road, with winds and trying to ride efficiently (as opposed to on the jig), I was pulling down into the bars and rolling miles forward on the saddle. With a slightly longer and lower stem, and actually making sure I used the saddle to take some weight, the hand discomfort went away, and I got much better glute engagement to boot.