A Dlask 0.920 12.5" barrel really isn't that heavy. I've slung mine while tromping through heavy bush deer hunting and you can barely tell it's there. Off hand shooting is perfectly comfortable. A longer barrel is obviously going to be heavier and biased towards the front a bit more balance wise, but I don't find my 18" heavy barreled 10/22 to be a "bench only" gun, still very doable for off hand shooting. The 10/22 Target specs at 7.5lb from the factory, that really isn't heavy...and that's with a 20" heavy barrel. If you have problems carrying or shooting that, then you will also have problems carrying or shooting most average centerfire rifles or shotguns.
There is no reason you can't shoot bulk ammo with a Dlask barrel. Like hoyt said, Dlask does have two chambers available. I've had a 9" (not Dlask) and a 12.5" Dlask, both with Bentz chambers, and never had an issue. Out of probably 20 different ammo types I've tried, I've only had 1 that didn't want to run 100% (Winchester target, everything else from the very very very cheap stuff to higher end stuff has been perfect, not a single malfunction). The only thing you can't run with a Bentz chamber is Stinger cases (as they are longer).
As far as noise goes, the 12.5" has noticeably more report than a 16+" barrel, but it's still fairly quiet. Standard velocities without hearing pro isn't uncomfortable. My 9" was noticeably louder, it's still a rimfire (so it's not thaaaat loud), but the report is sharper and more uncomfortable without hearing pro. The Dlask XB5 definitely helps direct that noise forward though. I'd strongly recommend Dlask, been very happy with every product I've bought from them, and plan on building another 10/22 on a DAR22 receiver soon.
Gillen1 I'd definitely recommend the 12.5", after my 9" build I talked to a few people (including hoyt) and they told me the same thing. The 12.5" is a perfect compromise between size/weight/accuracy/noise/balance/etc I find, if you are wanted to build a compact gun. I carried mine around up north this year for grouse and it worked perfectly. Accuracy has been great, and 0.5" (or better groups) at 50 yards are the norm consistently. I've shot it out to 200 yards with no issues. My 9" really opened up outside of 50 yards.