I'd make some easle backs out of .040 Aluminum. Put a 1" bend on the edge and attach it to the PVC with VHB.
I use 6mm coro cut to an easel shape. I split one side of a flute about an inch from the edge and adhere it to the back with good DF tape. I'll take another 2" strip and with velcro on the ends which are also slit to bend, attach one end to the figure and the other to the easel fold out.
If you need some more weight, cut a coro triangle and cut and fold two edges. Attach it to the easel wing at ground level with velcro strips and place whatever weights you might use on that base.
I usually make my figures routed out of gatorfoam instead of sintra so they are easier to handle and support but I have done a couple with sintra also.