Would you really want a “carry case” with that length of boat? As the case would be at least another 3 to 4 inches longer than the boat itself to allow for internal padding. Now thats one hell of a box, let alone what vehicle do you transport it in.
Thats size of craft is surely at the limits of what is “carryable” so to speak, especially in “one piece”. Surely it would be safer to have it split in half and bolt the 2 sections together poolside, for ease of carriage and personal safety in carrying it.
its either that or use a 2 axle trolley to “tow “it to the pool/lake, then you also need sufficient “helpers” to assist you in lowering in to the water.
“IF ” had no choise but to cary it in one piece, id simply make an open frame “stand” type base, to which you can clamp a couple of axles to, once you arrive poolside , but you’d still need helpers to do all this, as you have to think of its overall weight as well as length, plus all the delicate bits you dont wish to break off as you haul it out of the back of your vehicle.