How to measure, determine the "thumb-hole"?

[t_jones98]

Want to make a custom stock for my Nitro Venom Dusk.  I actually really like the composite stock, but need to elongate as well as want a pistol-grip/thumb-hole.  I'm about 6'4" and have an even longer wing-span. 

My main worry isn't necessarily about the butt of the stock, I can fabricate an adjustable piece for that.  It's the thumb-hole.  Measure twice, cute once right?  What the heck do I measure?  What angles? 

With the artillary hold in mind, how do you determine where the hole should go?  Oblong/oval or carved out round? 

Does anyone have any patterns they would like to share?  Obviously I will have to make mods due to my size, but looking for a place to start.

Thanks,
Jonesy.

[Motorhead]

Having purchased a RAW unfinished TH stock, once in hand ( Literally ) went about grasping and holding stock changing shape until GRIP and Thumb hole felt correct.
Really not sure a generic shape or pattern exists thinking such a style of rifle grip is very much like a bowling balls finger holes   

[t_jones98]

Thanks.  I tried to get a hold of Rocker1 from this post: http://www.gatewaytoairguns.org/GTA/index.php?topic=24460.0 but have not gotten a response yet.

Looking at the fourth picture down, simply beautiful. 

I did find some 1-1/2" pink foam that I am going to try to make a pattern from.  I know it's not thick enough for the main part but it should give me an idea as far as lengths and the grip.

Jonesy.

[t_jones98]

1 1/2" Styrofoam, table saw, jig saw, sharpie and my trusty Rigid cordless.

Thumb-hole feels pretty good.  Thinking it's going to be a LOT harder to take off material from walnut or other hardwood stock than the "pink" though.

Jonesy.