The Superlight uses a .625 diameter FSB at the gas block area, so your RRA won't work unfortunately.  You might talk to YHM as I saw in another thread tonight that Larry had offered to make one up for the Superlight.  The other option is to find someone wanting to sell their preban superlight FSB but that might be more trouble than you want to line up the taper pin holes.

Jason

Swapping FSBs, even on barrels with the same diameter in the FSB's mount area,  almost always involves extra work as you're NEVER going to be assured that the taper pin holes are going to match up.  Most likely they won't.

That leaves you with two possible ways to proceed:

1:  Mount the intended FSB and drill new holes in the barrel, using the FSB's holes as the guide.  
This isn't recommended as you're sure to be partly into the original holes, and no way a drill bit
is going to drill straight when it's partially into an existing hole.     Besides, you don't want to drill
out MORE metal from the barrel.

2:  Get the taper pin holes in the FSB welded up, Dremel the welds down,  reparkerize the FSB,
and install the FSB to the locations of the existing holes in the barrel.   This takes some specialized techniques and tools.   A small milling machine is really pretty important to do the job right, but maybe you could make do with a drill press if the table is big enough.   The idea is to locate the barrel holes, lock the barrel in place, mount the new FSB, and drill in that spot, then run the taper pin reamer through until it just touches the barrel's holes on the insides.

Really, it's not a job for the average guy.   It's a gunsmith's task.   I can do it because I'm an amateur but school-trained machinist.   And I've done it a couple of times.

CJ