HI I don't know if it's any help but I am working, ableit slowly on a similar project in a smaller scale.
I have taken two vinyl Kenner type 'Toy' action figurines, posed and locked the poses with superglue, filled the joints with epoxy putty and blended it in and primed the figures
Please go to my album "The hunter and the hunted, Predator and Dutch.
As you will see from these poor phone cam pics I have posed the original Predator in an abseiling type pose and Arnie, as Dutch will be on the other side of the tree amongst the mangrove roots half in and out of the water.
The 'tree' is aquarium Bogroot screwed ino the base from below for a permanent fastening with a cantilevered constuction.
The rocks are chunks of cork painted in blacks and browns and the brown forest floor leaf litter is coir compost and pva glue.
The creepers and vines are copper wire with supergue dribbled down to stiffen it and moss used to give the appearance of epiphites and creepers.
I have so far punched 2,500 leaves from brown paper to use on the model and may yet illuminate the side of his helmet with fibre-optics.
Good luck with yours keep in touch