I wonder if anyone has tried polyurethane casting resins instead of epoxy for levelling?

The stuff i have used in the past ( for casting not machine levelling) has the viscosity of milk and is designed to run and fill all the voids in a casting, i would imagine it would be better than most of the epoxy resins i have come across.

Its tough too and will take fillers and reinforcements if you want to use them.

http://www.benam.co.uk/products/plastic/

just a thought...