Too heavy? Y'all need to hit the gym. Once I put transom wheels on my boat I never dipped the trailer ever again. No wiring issues, no rust, no wheel bearing issues, not dipping the trailer is a plus. My boat weighed 500lbs (226kg) ready to go into the water. Took two people over beaches, but with a remote controlled electric winch on the trailer I could launch and recover solo on launch ramps aka slip ways.
I would recommend only using Wheeleez tires or tyres if you spell it funny
A 42cm tire should make it smooth rolling. https://wheeleez.com/wheels/
The legs might be able to be purchased but can be fabricated just as easily as buying a set then having to modify them.
Cramming transom wheels, who knows what else, plus a kicker is going to be a tight squeeze. For me I figured out the best way was to keep the kicker over the port tube on a sliding bracket. Then if needed, remove the port side transom wheel and slide the kicker over. Well fortunately I never needed the kicker, but it is reassuring to know I always had a second engine.
This was the first test using a steel bracket. Once it lived on the boat, I bagged the engine power head in a heavy duty contractors bag to keep it dry, and tied the back of the leg up to the port side axle of the transom wheel. Everything rode solidly through rough waters.