Similar situation here … weight limits are stated on the hippo bag (only supposed to 1/3 fill if disposing of earth or rubble, if green waste, then I think you can fill them). We just sprinkled grass cuttings over the top of a rubble and earth filled sack 😉
It didn’t split when the lorry came to pick it up. I think the big bags are smaller than all but the smallest skips. We didn’t get a skip license. All in it seemed to be less hassle than traditional skip hire.