I really like my CASV-MT on my BCM midlength. The only downside to the CASV series is that after prolonged firing sessions, the handguards get too hot to hold with bare hands.
I like the Casv system, works well on SBR build that I have. Should work well on a mid length just as good. Weight is moderate, and if you don’t want to run too many accessories or rail panels, remove the rails with allen wrench and only use the ones you need. Advice on this though be sure you run it with gloves, the Casv will get hot with sustained fire. Ask Grant for more info since he has stated he has been running the Casv on one of his SBR’s for a couple of years through training classes and such. He might have some more pearls of wisdom.
+1 Fan of the CASV. They work great with an Eotech. Only down side is finding a BUIS that fits on the available rail space. ARMS 40L worked great from me, YMMV.
Also BUS for this system that works really well are the Troy rear/front. Omit the front if you have an FSB of course. The rear fits perfect like it was just meant to be paired with this rail system.
I used to run the CASV-S which is designed for midlength gas systems. Nice piece of kit except the 10:00 and 2:00 screw mounts are useless (mounting a rail there puts it too close to the top rail). I punched them out and milled them into extra QD holes since I like my sling mounted closer to the receiver. The stepped foreend lets you run thumb-over if you want. I chopped the back of mine to fit the MBUS. I run the VTAC/Troy now, so I gave it to my buddy to replace his normal CASV, but if I had the requirement to keep the delta ring etc I’d stick with the CASV-S.