It was just me and I'm barely 160lbs. Your also correct that having passengers makes a huge difference. Which is yet one more indication the C is underpowered. (Or at least it is in my opinion.)
How do commercial trucks handle that on-ramp? I know of a highway on-ramp that virtually no car can do at merging speed. Not because it is steep, rather it is built very small and without banked turns, so everyone has to go slow until the last 60' or so. Apparently it was one of the earliest cloverleaf style junctions.
Yes, I received the durability survey too. In fact, this is the 3rd durability survey I have received on this car from Toyota. I try to be mercilessly honest even though I love my Prius C.