DST is not a good back mount regulator no mater what people say it has a turret but still has bad hose routings and hits the back of your head I personally use it for stages or side mount and even for that there are better choices. Couple it with bad materials used in service kits you get a long term expensive regulator.
I would go for a ds4+xtx50-s, fsr is super nice if you are diving a single tank but the extra price for it might not be worth it for you.
I would go for a ds4+xtx50-s, fsr is super nice if you are diving a single tank but the extra price for it might not be worth it for you.