Mine's an 11" barrel. The thing about the Yankee Hill Phantom is that it's super thin and light weight. Seems like pretty high quality steel that (I believe) you can mount a sound suppressor onto. The 4 piece (Bulgarian-type) flash hiders (that I've used) are quite a heavy chunk.
The Phantom was doing a really good job of suppressing the flash of regular Tula fmj and hp, which are known for belching out big, bright fireballs.
Before I started shooting, both Yankee Hill and Manticore confirmed that their muzzle devices were @ 0.311" in diameter and I had no problems in that regard.
Absolutely -- the 4 piece are HEAVY, but do a very good job with flash suppression for sub 13" 7.62x39 guns -- personally, I'd rather have a longer barrel, but in the AK world there aren't too many affordable AKs in the 12-14" range... Mine's on a 10.5" M92 PAP.
The YHM Phantoms and Smith Enterprise Vortex are generally what I find to be the best in flash suppression.
Precision Armanments muzzle devices are expensive, but the AFAB and the EFAB are by the far the best options I've found for both flash suppression and brake/comp performance -- concussiveness is also much less than most other brakes/comps.
PWS's FSC30 is a decent cheaper option and I'd personally go w/ that before manticore's night brake -- if only b/c the FSC's don't have any porting to the topside which puts flash directly into the shooter's vision. It's optimized for .308 and larger than their FSC47 that's optimized for 7.62x39 (so probably more flash comparatively), but has the correct threading for your barrel.
Barrel length just noting that anything shorter than 12.5" or so you might have some overpressure considerations/limitations on devices but unsure of exact cutoff -- on 5.56/.223 guns some aren't rated for short barrels starting as soon as 14.5". And that anything less than 16" on AKs will have at least some unburnt powder bits that generally will "glow" regardless of effectiveness of muzzle device on overall flash signature. Even some 16"+ guns have more unburnt powder with some loads than I find desireable...