I believe the Hobie warranty normally covers materials and workmanship. Proper use of the proper cart is the responsibility of the user. The older carts have shorter legs and do not always extend all the way through the scupper tubes on some of the newer boats. This is what tears the scuppers up. If Hobie is replacing the hull on this for only the shipping charge, IMO, your friend got a very nice early Christmas present from Hobie!
Your friend will put a hole in his new boat also if he doesn't get a longer legged cart or at least extend the legs on his old one with PVC or something comparable. Here's an old cart, for example with extensions and eyebolts that can handle any Hobie hardshell kayak. The eyebolts are used to lock the cart in position on the boat if desired.
All new carts all have sufficiently long legs to handle all the boats, and include a locking pin and domed tops for safe retention and easy insertion. Wheels are not necessarily interchangeable. You and your friend should both use the cart that meets your launch conditions.
