Yes, this is exactly how the outer rails are milled out. There is a rabbit on the inside that clears the plank and canvas. The top fits tight to the rib tips. when installed it will clamp the canvas and hold the canvas tacks from backing out. The profile is a bit more complex than cutting a 90* rabbit in the back of 3/4" stock. You may need to ask around for what the profile should be. I can take pics of my original rail profile. But that is off of a 1922 OTCA.