The design looks cool, but what happens to the part of your forearm that is below the barrel/cylinder gap when you light one off? Steel sleeves may be advisable given the pressures at which these guns operate. Or maybe you shoot these things with a bipod or a sling loop around a tree. (But watch for flying bark!)
I have always been leery of revolving rifles or long-barrel revolvers with detachable stocks. The consequences of chain fire in percussion revolvers pretty much doomed the design. While I don't expect chain fire in cartridge revolvers, you can't ignore the high-pressure gases in the X-frame models.