I use the standard cart for both the AI and TI. I always roll the boats in and out of the water on wheels. It's easy to snatch the wheels out with the amas collapsed. To get them in is a little more difficult (especially solo with the TI), but the wheels are not too hard to manipulate under water. In my case, I collapse the amas, leave the mast in for counterbalance and jerk the near side out of the water, supporting it against my bent legs while reaching under with the cart. Takes a little practice -- works with both boats and is easier than dragging the boats ashore.
For higher volume wheels (Trax, Trax 2, Heavy Duty), pirates method of adding water is very simple. It's a tried and true adaptation of an old farm tractor trick to add cheap wheel weight for added traction.
1. unscrew the valve
2. submerge the wheel in a bucket of fresh water until mostly full (if your wheels have a steel hub, add environmentally friendly antifreeze to prevent rust)
3. stand the wheel upright on the ground (valve stem up) and rotate it spilling the water out of the open stem to about mid hub +/-
4. insert the valve
5. With the valve stem up, add a little air to spec.
This neutralizes the buoyancy, without impairing the operation of the wheels. The wheels become heavy out of the water, but you don't have to lift them far and they have an insignificant impact on boat performance.
I haven't used this method on the boats since I use standard carts, but I've been using this for years on small tractors, and pirate has demonstrated its effectiveness with his AI.
Just a note here about shortening the cart legs by adjusting the cart clamps. Hobie recommends the cart legs always go completely through the scupers and out the other end; scupper tubes are thin and fragile and can be torn by transporting the boat without the cart legs extending completely through the scuppers.