for the top or bottom? i am making the James Bond 007 995 and just tonite was researching how to put a bottom rail on it. problem is i only have 1 inch of space from the front of the "stock" to the u clip that holds it down, so i had some extra pict rail and cut it to 1.25 and then wrapped the 2 pieces of stock together, made my screw marks with a hot nail and fashioned a base plate out of the bottom of a glock magazine that i had, so basically from the bottom up you will have your pict rail with the screws going up into drill holes in the stock, into the holes in the stabilizer plate inside the stock then small nuts holding it on.
What about trimming a small channel into the bottom of the stock and running a flat piece of metal up to the bolts that hold the stock together? (Am thinking straight up between the halves of the stock) The bolts measure about the same distance down from the barrel and therefore you would use the same length metal front and back to get a surface to mount to that won't be sloped like the bottom of the stock. You will have a gap btween the front of the rail and the stock though. I am also wondering if it would cause a problem with the tab that attaches the front of the barrel to the stock.
that was a photoshop mock up of what he was doing. the final product does not have handle. i think my way will work ok, if it does not i'll just fashion 2 alum plates one inside the stock and one between the foregrip and the stock and put my bolts up through the bottom, either way it's the same, easy.