The problem is your solution is awfully inefficient ... the reason you'd want to use a rail based light is that it WOULDN'T be a mag tube clamp (requiring removal for cleaning) ... if you get a mag tube rail clamp, then use a DD rail mount flashlight holder ... it's a redundant system for no real benefit as I see it, as neither of the items is quick release ... IMO you would be better off just getting a simple magtube clamp mount if you're going to go that route.
You see what I mean though? You're using 2 parts to perform a job that is better performed by one part ... a railed tube clamp with a DD rail grabbing flashlight mount is going to be more complex, expensive, heavier and bulkier than a smaller, stronger, more efficient one piece mag tube clamp light mount ...