What is the gnneral rule of LOP for a double rifle?

My bolt rifles are ordered with a 14.75" LOP, usually HS Preccision after market stocks for model 70's and model 700's.

My shot guns are set up with 16.25" LOP.

What would be my (guess) LOP of a double rifle? My only double rifle todate is a german 8mm. I have a leather slip on pad on it and it's still way to short.

Before I order one I'll get fitted properly, but I'm just curious. The other thing, are there any vintage doubles out there that will fit me? I usually see a LOP on a double of between 14-15".