Hey there - welcome to the forums... So, as far as I’m aware, the best way to start/Stop a RED DSMC2 system are via R/S or BNC. With the Blue Command Cable to BNC, you can use your B Box the way you mentioned, but you can use use the standard RED timecode breakout pigtail - the white BNC in there is run/stop, but I prefer the BBox. Alternatively, with 3-pin Fisher R/S, you just need a camera cage that will allow you to use it. On House of Cards, we used the Tilta DSMC2 “A” cages (with quite a few issues), but I’ve had a lot of success recently with the Wooden Camera top plates - just make sure it’s been sent into Wooden Camera to have the internal board upgraded as the first batch has several issues rolling and stopping the camera. Another good system is the DXL-M system from Panavision - very reliable roll stop over R/S. 

Also, there are native Blue Command to DSMC2 CTRL cables out in the world (like from Media Blackout) - you just need to make sure they’re designed for the momentary low pulse of the new RED protocol, and not the continuous signal of DSMC1. If the cable is wrong, you can always use a pulse adapter, but that gets annoying. 

Quick follow up on the situation. I contacted a local cable maker in Montreal (Canada) and left my MDR4 with him for 6 days. He managed to create a 10 pin 1B lemo to bnc connection that works perfectly with any DSMC2 body. I tested the system with the wooden camera box and the pigtail cable and everything works A1. No adaptor needed. 

One of the key factors is the type of expander, and the triggering system, the base expander uses the schmit triggering protocol, jetpak and other versions uses the more contemporary Arri/rs (also Preston) protocols