I am also in the process of having my first true custom wood stock made. Ended up sending an existing factory wood stock that fits me well and I really like to the gunsmith to use as a template/guide with regards to:
> Grip dimensions
> Grip angle
> Comb height
> Fore end dimensions

Utah708 has a much more complete list above. However, these were the points that typically cause me angst and were of greatest concern to me. I do not know Mr. Simillion. However, he has an excellent reputation. Assuming these type questions will eventually come up during the course of your project.

Good luck !