I've started SMing this summer and also made a DIY rig out of my BP/W. In my case, after looking at the Nomad at the Tacoma Dive Expo. I made my own outer plate to cover the wing to prevent tacoing. I want to bend it a bit more but it does the job. I'm also tweaking the small bungies holding in the wing.
I also made a butt plate but I have found it hard to clip on to. I need some larger bottom snapbolts and I also bought some thinner gloves (lobster gloves and clipping don't mix) and I also experimented with the butt plate D ring positions a bit. Fortunately, I feel I can clip off to the hip D rings and maintain fairly good bottle position so I just took the plate off for now. This has caused a lot of underwater swearing though.
I attached some bungie to my backplate with a snapbolt on the other end that I can clip into my chest D rings. When not in use the snapbolt clips into my hip D rings. This allows me to don the rig, reach down and unclip the bungie and then reclip it. The bungie I have now is too thick and I plan to replace it with thinner stuff. I may experiment with this a bit as having so many snapbolts on the chest D rings begins to cause a clutter.
I am using Steel 72's tied off with rope connections for now. I don't want to use bungie for the top snapbolts as I shore dive and want the option to enter and exit carrying my bottles clipped off. I think I will replace the bottom snapbolt connection with bungie though to get a bit of pull space when I clip off to the buttplate. I'll wait till I get the bigger snapbolts to decide that though.
For hose routing with a wetsuit; On the right I use a short hose and a snapbolt just off the second stage (held on with tear away bicycle tubing) which is clipped off when not in use. On the left I use a normal length hose routed behind my neck with a bungied second stage (just like a Hog setup). I also have a LP whip with a bend in it about 8 inches from the connector (the bend is held with a piece of bicycle tubing but I think I will make a brace so that it won't kink). It routes up under my arm and then down to the inflator on the wing. When diving dry I will just run another whip off the left tank.
So far so good. I've done single tank and double side mount dives and am pleased with the stability and ease of operation. Clipping the bottom clips is an issue but I'm pretty sure bigger snapbolts will resolve this. I keep working at removing weight so that I use minimal air in the wing but with an 11/8mm wetsuit I will always need some at depth.
Cost: $20 aluminum plate and a few bucks for bungie.