The Tom Cat 30 walk around has used a High thrust 8 hp for trolling. This is mounted in the center of the bracket.
On our Tom Cat, I made a motor mount for our 3.5 hp dinghy motor which fit on the fittings for the dive "T" boarding ladder. This mount was out of Starboard, and was fine for the 3.5 hp--I would want something substantially sturdier for an 8 hp. The heads of the bolts were squared off and just fit perfectly in the SS slot for the boarding ladder.
For my Caracal--single engine cat--I bolted an "L" bracket on the swim step and it is quickly removable. It would take an 8 hp. To adapt to the Tom Cat, I would set up 4 points to bolt the bracket int on the Aluminum bracket. Those points might have to be welded on. I used a similar type of system for the bow roller on my Cal 46 to make the roller removable and reversible. I mounted a 1/2" thick SS plate on the deck, and tapped it for 1/2" bolts which were flat head (use allen socket, rather than slotted or phillips type of screw diver.
I don't think that the weight of an 8 hp would make a lot of difference, and would be do-able....
Sorry for the out of focus shot
If you wanted a permanent installation, then weld a vertical member to the outboard bracket--may need side gussets. Put a wooden block in the center for the required thickness for the motor clamps. The shaft of the kicker would have have be the same length as the main motors.
