Thank you very much, Loy.
And I forgot to mention: while most of the people in the crowd are adults, there are many children and probably a few R2D2 robots. This is going to be an interesting project. I suppose I will start out with collisions in my motorhome where there is just me to damage. Then I will add in other factors by inviting other people in and putting random boxes down to simulate a changing environment.
Then I might bring Groucho outside and see how he handles there, with me close by with a remote cut-off switch. Unfortunately, I have to carry him in and out of the motorhome. This puts an upper limit on his size and weight, though I will make him able to be split into multiple pieces if possible.
Jay