Thank you for your suggestions and replies, very helpful.
I like the "slaughter design", I will have to find the right materials to assemble it, althoughI will not use an hobie scupper cart.
Actually, I usually launch from beaches of soft sand and until now I am dragging the kayak hull across the sand withoout the cart. But I wish I could find a more relaxing way to start the trip !
This is why I am very glad to learn from SDN that the 30 wheels can be stowed into the front hatch: I decided to buy a wheeleez cart with the 30 wheels, which I can use as is at first.
I am not impressed by the hobie cart 2-30 design, so in the next future I will have to find a way to fit the "30" wheeleez on the "Egalis" kayak cart which I am using at present with its pneumatic tyres.
This cart is my favourite, small, lightweight, can be easily disassembled and stored and it fits the AI hull quite well.
However I am also going to try and build a different cart design. Will keep you updated.
Thank you very much to you all.