I put this set up together for dives where I wanted some redundancy; for testing out newly built reg's, deeper reef dives and deep wreck dives where I wanted a bail out on bottom gas (I carry a 5 litre deco gas bottle with a 40% mix - so it's good above 90 or so feet.) Of course the H valve doesn't help with an OOA situation.
The valve is a normal Dive Right din valve with a H valve addition. It allows me to add a second reg with all the bit and pieces, pressure gauge etc. I put it together with the VDH backplate and found that the H valve needed to be turned around as the 1st stage of the Scubapro Mk 2 was hitting the backplate. I don't like it turned around and will look for something with a small 1st stage. Wouldn't mind an old USD reg - if you can think of a suitable model with small first stage please post.
I'm going to put a Zeagle 18 lb wing on the plate, but will wait until I see the VDH version.
The turned around 1st stage is not a good set up for wrecks.