I too, mount my outboard directly on the transom. What I do is mount the engine (2.5hp Suzuki) as far outboard as my wooden pad on the transom allows. I also slightly offset the tiller and prop so it’s driving slightly off-centre and outwards and not directly backwards. This also improves clearance a bit between the prop and rudder. I also stuck a bit of foam on the side of the tiller to act as a soft-stop when pushing the tiller over. It worked well until it fell off. But with the first 2 measures in place, I haven’t managed to mangle the rudder.