First, I would caution most severely against flying practically any aircraft without proper training; accidents often result. A real shame to break an aeoplane or lose your life so needlessly, perhaps.
Second, TopBunk is trying to lead us badly astray with:
The single engine performance was still 200-300 fpm on the go-around
This is almost certainly a result of the instructor setting a hopelessly high simulated zero thrust on the 'inoperative' engine; at MTOW, the typical flying school Cougar will struggle to go up at all.
But what should we expect from one who acknowledges:
retrospectively I suspect that a load and balance calculation would have made us illegal
The time to establish that, was prior to the flight, which you should well have known, if at 1179 stage.
Certainly, if you fly any piston twin without proper training, you are most unlikely to be able to handle an engine failure near the ground and fly the aircraft accurately at blue line speed whilst doing the drills.
