I does not really matter what you have to do. It's an Airsoft part worth $99 and it is ALWAYS going to move around on you sufficiently enough so that you could NOT rely on a laser to be dead on each and every time.
The only thing that this getup would be useful for is a flashlight or a forward grip.
If I got one, this is what I would do. Get it from ebay for $99.00. Then, weld the whole thing together - remove the ugly screws that hold it together. Cut the extended rails off, so that it looks descent.
Smooth off the welds, bead blast it and then have it coated with black teflon.
The way to properly mount it would be to drill 2 parallel holes for the upper blocks and drill the holes straight thru the receiver. This way, the unit becomes part of the receiver rather than appendage on it.
Then and ONLY then, could you say that the unit is HEAVILY modified, worthy of being on a military rifle your life depends on.
AND - this goes without even knowing the metal composition. For all we know, it's pot metal that will get brittle at 10F and shatter. I'm sure that at $99.00 it is not quality metal.
Now, it's a sound concept - with poor execution and imporper materials. Now if ARMS came out with something smaller, milled from bar stock at say $350, I would be all over that.
Better yet - why don't I get the CNC up and tunning and start a small business? Maybe that is what it's going to take. I will make a prototype and see if there is any interest. Ah - another weekend project coming - and the wife in the backround is starting to fume. Priorities ... priorities.
-TH