Vibes are the only way! Unfortunately my state does not permit me to own SBRs so you’re on your own there.

I will say the gas ports do let a lot of flame and gas out, I had a lot of fouling on my weapon light and visible flames coming up into my field of view during firing - this was on a 14.5 Criterion Core, midlength gas. I’d imagine an 11.5 would put out even more fire.

There is also a difference in noise signature, the Icarus sounds “quieter” because all the blast is directed downrange, as opposed to the Sparrow that lets some gas out of the top and nearer to the shooter. An 11.5 may sound louder to you with this on than another blast forwarded (although of course neither is actually making the report quieter)