I'm quietly jealous of your new rifle.
Good for you!!

Two forend options come up for me around thoughts of a good user rifle.

For one, I've seen numerous and handled a few rifles with longer than typical forend wood in a fairly standard splinter shape. I like the way the bit of wood works to fill the hollow in the palm of my support hand when reaching up the barrels for a good grip.

Also there's the (and I'll qualify this as *ever so slightly*) slight semi-beavertail forend, also done to the longish end of the spectrum.
I've seen a few older (british) Rigbys with that kind of treatment and it actually looked quite good. I haven't had the opportunity to handle a rifle with such an arrangement, but I can imagine it's going to depend on what your personal measurements are like.
In terms of bicycle fit, I ride a 59cm top tube with about 110-120mm of stem. That's a bit of a reach for most guys my size (5'11") but I have longish arms and generous hands.

Think about what tools, shift knobs, computer mouse shapes... suit your hands and sense of style best and consider that while you're at it with Butch. The action shape of his guns can handle a fair range of stock styles without looking out of place. I think you'd be able to do just about anything with one of his guns without killing the looks.
I've even seen full stocked DRs with schnable forend tips, a Searcy with it's 24" barrels and a slender manlicher style forend in a light caliber like 7 or 8mm would be really neat!

--Tinker