FWIW, I prefer stretch in a tow line to reduce shock to your body/boat. You can add this by securing a coil of bungee cord around the line, or by using a stretchy line in the first place. Most kayak tow systems provide strength well in excess of what 's actually needed, IMO. For kayaks you generally need a line that can handle tens of pounds of force, not hundreds or more. The line provided commercially is usually much beefier than necessary to make it easier on the hands, prevent rope cuts, provide abrasion resistance, etc. Also some incident management courses use tow lines to lift kayaks over rocks, and I have even seen people use them as a climbing rope (not recommended) to negotiate rocks on shore, so the lines may be put to tasks far above and beyond what the manufacturer intended for just towing and are probably intentionally "over built".
Despite my earlier remarks, throw systems CAN be useful from a kayak, in specific situations. For example, if you have a swimmer that is not in surf (lines in the surf zone are an entanglement hazard) but you can't safely reach them with your kayak -- places such as sea caves, complex rock gardens etc., they can give you more options. I suppose you could find a similar environment near a rock jetty in Florida, but at some point you have to draw a line. For example, if I was standing on a rock jetty and throwing to a swimmer, I'd prefer to be wearing my helmet too, in case I slipped, but having too much rescue regalia has its own inherent problems too, especially in the heat.
Charles your tow/throw system looks like a good one, I have taken Jeff Allen's incident management class and he knows his stuff. I would personally forgo the "throw" component for an EC to have my tow system lighter (and cheaper) but I could see a combined throw/tow as very useful for other environments as discussed.
A line is also great to prevent the tide from stealing your kayak, or to deal with Choko mud (if you can tie-up to a tree). A towline does make a great laundry line, but I'm not taking the time to hang laundry during an EC!
Greg
