Try to keep the simple, slim English stock layout - ok, so raise the comb a bit to manage the scope better.
If you can get the dimensions of a Highland Stalker, it is just about the perfect balance in design and you will be mirroring an actual Rigby. And see if your stocker (you?) knows how to apply alkanet root coloring. It is what gives English guns an rifles that lovely red hue. It also will really accentuate the grain. Otherwise, you run the risk of it simply looking like a tricked out American custom Mauser rather than a special order Rigby with fabulous wood.
Diggory Hadoke provides recipes and instruction for making gun stock oils.
www.vintageguns.co.uk