I’ve done the circuit twice with a kayak – a tandem and a single and also with a canoe. The canoe was easiest, because I built a big cart with 20 in. bike wheels that did a great job over rough ground and was quick to set up. Just plop on top of the packs at each launch. Not so easy with kayaks!
Most kayak carts are not built for this type of use although they can be made to work ok. For the tandem, I broke the cart immediately but was able to rent one at the Park instead that was quite sturdy, but bulky. On a tandem, one can lash outsized things on the deck between cockpits. Our boat and gear were heavy. With the single kayak, I used my standard metal-framed commercial cart that took a beating but did ok although it was hard on the boat. The usual way I use a cart for a short hop is to place the cart aft of the cockpit and pull on the bow, being careful not to drag the stern. The adds weight to the load on your arm but it is at a reasonable height. Some of your portages you will be long, so you need to put the cart under the centre of gravity – approx at the cockpit- to reduce arm weight. This makes the bow quite low and you are tall – hmmm – you will curse that low bow pull height unless the cart is taller than most of them. Also definitely rig good a good strap around the cockpit coaming – the wheels often don’t want to go where the boat is being pulled.
I’ve nothing against solid tires- one less thing to go wrong. I had problems with tire inflation on my trip – does the pump actually work on the valve (valves on some plastic wheels can be too short for mini-pumps to latch to) and can a flat be field repaired?
I’d suggest buying (or building) one, Bob, only because your ‘one time use’ is severe and probably amounts to more ‘abuse’ than most carts will ever see in their lifetimes! Many a cart has broken here, even after Parks put in weight restrictions and upgraded the trail surfaces.