I did not modify my gas systems, no noticeable difference on brass marking or ejection pattern/distance from M1A 22" or the 16" Socom. I read somewhere back pressure only increases 5% were most cans increase 30%. But in my old age I could have been reading about pellet guns.
As for the LH threads mine has never loosened up I don't have a RH can to compare it to on a rifle. But LH on my pistol will stay tight all day, RH thread need re-tightened every 3-4 mags.
The endcap vents on the OSS cans are angled, so they will physically rotate the can tighter on LH thread each time the weapon is fired. This is why the OSS system works great with LH threading but pistol caliber HK's without vented endcaps can still walk off of the threads.
An OSS .30 cal can is on my short list, whenever I start buying gun stuff again.
Mile High Shooting has deep discounts on some Helix cans.
I like mine a lot.
David S.