First things first: Rebreathers can be a pain in the ass to transport. Gladly, the IDA-71 (like the Mark-15) seems to have been designed to fit into what is called a "Fish Bin", which is a heavy duty plastic tub that's used on commercial fishing boats to carry fish back before it's sold. These stack when turned one way, and nest when turned 180 degrees. They cost next to nothing, and are indestructible. They can be used for washing, bubble-checking, sitting on when eating a Sandwich, and a multitude of other things. Get 'em at your friendly commercial fisherman supply place. Hint: Head down to the scummiest part of the harbor to the scummiest dock and look for the cats all hanging out near the rotting lobster-bait. That's where you'll find the supply place.
Just a vanity shot: Yes, that's actually me, diving the original Franken-Rig. Notice the clean sleek lines. Hey, the rebreather is pretty sleek too!!
Seriously, the rig is exceptionally well streamlined, and is a pleasure to swim.
How do we add a harness? Well, if you are like me, a simple, loop of parachute cord through the original harness loops at the top make easy to fabricate harness attachments for the shoulders.
Detail of the loops of parachute cord. This actually worked great.
Bottom harness can re-use the original points as well.
Did you say something about lead on the harnesses? Yup, just like a Mark-15, these need trim weight up top to balance the counterlung. I thought that these (4) 1-pound weights would do the trick. I was wrong. The rig needs at least 8 and better 12 pounds up high. That's all weight that can come off the belt, so it's not "extra" weight, just "redistributed" weight. It's hard to tell in this photo, but the lead is on the inside of the back-shell. I just drilled and tapped a hole in each block and screwed them on.
On Franken-Son I mounted 8 pounds internally. This is where the counterlung space is, which is not an issue as the counterlung has a lot of surplus volume and the weights take up very little of it's expansion area.
More sophisticated harness, you say? OK, no sweat. For starters, you do NOT want to use a backplate on this, as the plate will move the rig far enough from your back that work of breathing is affected. But since the rig is perfectly contoured, no plate is needed. Just bolt your favorite harness right on. I went to the hardware store and got these stainless steel nut-plates and oversized washers to make a bolt-on point.
Here I've used "Goop" to glue the nut-plate and the washer to the interior of the rig. This makes a well reinforced area to bolt to.
Here's what it looks like from the outside.
At the top, there are (3) tapped metric recesses already installed on the rig. I'm not sure what they are there for, but they are substantial. Just get three of the correct sized metric screws in stainless-steel and bolt away.
Here's a lousy photo of Franken-Son all ready to go. Some thought and a little bit of work will rig one of these chassis just right, and they are a pleasure to dive.