Yes, the tree is being used to do a variable resolution discretisation of the hypercube - so "important" areas have significantly more (and hence smaller) polytopes. Off the top of my head, the maximum volume ratio between the largest and smallest polytopes could be anywhere between $2^{10}$ or $2^{20}$. What you suggest seems fairly simple to implement, so I'll give it a try and see if it works alright. Thanks!