Here's how you fix that balance problem...LOL....That tells me lots. Balance out the weight, just make the bot do a lot more!
https://www.youtube.com/watch?v=8xiXzyIDXYw
Something tells me they will be in demand. Though once the big walls go up, they will be driving very carefully! I saw a stack of 6 capped in under 70 actual seconds w/ very lil' wasted movement. 4 at a time from the landfill, I'd be doing a layer of 4 in 2X2, go get 4 more, and 4 more, and layer the bottom all the way across 4 high~5 high first. Allow the others to cap and stack 1~2+Bin+Litter. They hit upon a really decent design w/ little wasted moves and really sturdy w/ a low CG it appears even though at max height.