In regard to the Weta. If it's possible at your location to break the boat down before heading up the hill it would be easy to set the floats to the side so it's only the hull and dolly that need to be pulled up the hill. The floats are bulky but could be carried up one by one apart from the main hull and dolly.
Having said that, I've needed help getting my Weta up a steep sand hill (I have parts to attempt a pully system next time I'm at that location) and I've struggled to get it up a steep paved hill (Cascade Locks dinghy launch area).
I was just thinking the other day that I wish