The original Fischer Canards had an semi airfoil canard at the back. Fischer's dad worked for Boeing and had access to their wind tunnels to perfect the shape. Too much airfoil and it would lift and too little and it would drag. Saw them run many times and they may not have been absolute fastest out there but Ed was a super driver and could corner 1 ft off the buoys consistently so nobody could catch him. Several of my associates bought the fiberglass ones but the combination of lift, prop and weight distribution was very finnicky and proved to be less successful then the up and coming riggers that were much more forgiving. Ed had it figured out and was not that great in sharing secrets. Before the boats went commercial, any time the boats were out of the water, they were covered with a towel to keep those secrets.
You seem to have discovered the lack of lift with your test model. There is very little aero dynamic support at the back for the weight of the outboard. You rely too much on the sponsons for physical lift which probably drag too much at speed. You need to add something to fill the gap between the booms to give some aerodynamic lift at the back. Fischer ran fairly small sponsons to reduce hull drag. Both had a significant dihedral, probably 5 or more degrees. The right sponson had a steeper dihedral so it would grab the water and act as a turn fin. The hull ski's and their associated drag can be eliminated in that case. You will notice that the Zip and similar boats have their CG much closer to the back than, let's say an Eagle, which is why they can get away with skinnier sponsons. Their weight is supported with the centre ski at the back which starts just about at CG and is quite wide.
The Fischer Canard GG was closer to the back, probably near the front of the wing. Not much weight was put on the shoe at the front, except for launch which got the boat nose up and air flowing under the rear wing.
Lots of good video of the Unlimiteds flying over the water. Very little drag from the sponsons and they use the ground effects air flow (air trapping between the hull and the water) to great advantage. Fischer exploited this effect.
Good luck and congrats for trying something that no one else is doing.