I went back and did an experiment with different masses. In the first experiment I rolled a half-sized tin into a full-sized one. They rolled but not far. Half the amount of momentum shared between one and half masses should mean that they move on at about one third the speed of the small tin coming off the slope.
I then did the experiment the other way round. You can tell from the photo clipped from a video that the tins are still moving. They ended up out of shot. The big tin leaves the slope with more momentum which it shares with the small tine. The resultant common speed is much larger.
A big tin and a small tin will not leave the same ramp at the same speed. There are several issues there that will need some further exploring.
