I myself was wondering about the Rapid Pulse backrest.  Recommended with the Happy Bottom pad.  I/we are building the Mantunuck surf kayaks and are gathering ideas.  Have you any experience with the Rapid Pulse backrest? 

This thread seems to have died down.

Does anyone have ideas on how to mount the Sonic Back Band to a Shearwater 16?

I made a couple of tabs out of plywood with fiberglass on both ends. The tabs were bonded to the underside to the deck, but one of the tabs got broken off when the plastic adjuster from the back band pressed on it and I put my weight on the back band.

All ideas welcome.

--Robert

   I have the Rapid Pulse back rest. I estimated where I wanted the back band to be anchored, which was a little foreward of the middle of my seat. I drilled two holes in through the fiberglassed sides of my kayak, plugged the holes with caulk and then anchored the back band with quarter inch stainless steel screws and nuts. I took an ice pick, got it really hot by holding it over the flames of my gas stove, and used it to melt two holes in the straps where I wanted to attach them. 

I ended up supporting the back of the seat with bungee cord anchored behind the seat rest, which hold the back band upright in place. Otherswise it will flop down, and if you get knocked out of your kayak and reenter so that you're sitting on top of the back of your spray skirt, you'll have a double mess trying to get your spray skirt free and getting your back band back in place. I once spent a couple of hours sitting on my back band.

I also found out that I like the back band tilted backwards slightly, so the seat keeps me from sliding around but doesn't offer me much back support. This is obviously a highly personal preference, as I'm not prone to back pain. The back rest keeps me in place when I lean back to roll or rest, and I've been on a lot of four hour paddles and the main discomfort is not with my back but with my legs, which sometimes grow sore being in one position for hours.

If I had to do it over again, I might have installed  some one-inch cedar on either side of the seat with resin and filler, covered it with a layer of fiberglass and then screwed the back band into the cedar strip with wood screws, rather than punch a hole in the sides of my kayak. 

I have continued to fit and refit my Petrel since I finished it almost a year ago. I now use a half-inch closed cell foam rubber pad that I cut from an old yoga mat that my wife gave me as my seat. I keep it in place with velcro. This gets me very close to the bottom and, believe it or not, makes a real difference in the stability and feel of my kayak, especially in a following sea. I spent a few months adjusting the location of my seat, and each move a half an inch foreward or back really affected the handling of the kayak. I toyed around with water supplies and finally settled on a Camelback pack designed as a lumbar bag, (available online but rarely in stores) and I secure it with bungee cord before each paddle. The disadvantage of this is I have to pop off my spray skirt to get a drink, but I found having water on top of my kayak affected my stabilty.

So, I think the back band falls into one of those things that is highly personal and that will likely require tinkering. What is good for me is not necessarily good for anyone else. My Petrel now has all kinds of bungee cords and rescue cords (around the edges of the deck for T-rescues) that I didn't know I needed when I built it. So the stainless steel crews just add to the impression that my kayak has been used and is sea-worthy. 

Cheers, Bob

   Photos of how I mounted mine: