I have large hands (but not that large) and I have learned to adjust my two-handed combat grip so that I can manage sub-compact pistols pretty well. It's a slightly different grip with a revolver, because you can't position both thumbs forward, due to the normal 'leakage' between the cylinder face and the forcing cone.

So, the best way I've found to grip a revolver is to clamp the weak-side thumb back over the wrist, right at the base of the strong-side thumb. You still do the 'push-pull' thing (push with strong hand, pull with weak hand), so that you aren't really having to grip it like a vise with one hand. Because you are pulling with the weak side hand, and clamping with the weak-side thumb, you don't have to squeeze so much with the fingers on your strong side hand. You are pulling it into the heel of your strong side hand, so you get a firm platform that allows you to operate your trigger finger independently from your grip, so that it pretty much eliminates the tendency to 'milk' the grip.

Clear as mud?

I use Pachmayrs on my GP-100, and they work fine...but then, I can't palm a regulation size basketball, so your mileage may vary.

The Ruger Super Redhawk uses grips with the same internal attachment system, so they are interchangeable with GP-100 grips. The Super Redhawk, being available in much more powerful calibers, has larger/cushioned grips available for it, such as these Hogue Tamer Monogrips, available from MidwayUSA:

Hogue Tamer Monogrip Grips Ruger Super Redhawk, GP100 Rubber Black - MidwayUSA

The wrap around the rear of the grip frame, and add a cushion to the area of the palm that gets hammered the hardest in recoil. You can look around your local area, and if any shops have a Ruger Super Redhawk on the shelf, ask to handle the weapon and "try it on for size" to see how the grips feel. The weight and balance won't be the same, but you should at least be able to get an idea of how well the grips fit your hand. The Super Redhawk Alaskan (3" barreled "snubbie" in big magnum calibers!) also has the same mounting system.

Good luck!