Buoyancy tanks are great.  If you stroll through Richmond Yacht Club, you can see all kinds of El Toros with built in buoyancy tanks.  Some tanks double as seats, some even make it look like a bathtub.  

One issue I've had with the buoyancy tank(s) on my Eastport Pram is that no matter careful how I was about sealing it, there was some water that got in somehow.  Of course, it wouldn't come out, so I had to install drain plugs, which of course is another place where water can get in.  It's a circular argument.  Sigh...

Hello. I do not own a Skerry but I have had thoughts about doing something similar to this should I ever build one. Something that might be worth knowing from people who have sailed Skerry's is this. Part of the attraction of the Skerry is the mode in which you sail it by just lounging in the hull and shifting your weight as needed. Side tanks would put an end to this. Does the added buoyancy outweigh the loss of this?

I plan on still sitting in the bottom of the boat when the wind is light. I don't think the side tanks will limit that. Actually they will provide an arm rest. And when the wind is up I will just move my butt up onto the side tank seat, and still be able to move fore and aft.