So I did it using ROTF Voy Megatron toes instead. Took a small part from Crossovers Obi-Wan (partly because it was exactly what I needed, mostly because he was already in pieces after another kitbash he donated to), specifically, the dogbone link that holds the rear of the cockpit on his back in mech mode. Cut in half and modded slightly, this part yields 2 perfect brackets for the new fingers. Glued them in place on the existing Demolisher hands, they fold into the scoop in alt mode, hiding themselves fairly well. In robot mode they fold out and can form a grabbing hand or fist of sorts. Observe:
I have another pair of Megatoes (heh) on the way to mod the white Demolisher similarly, although I am fresh out of Obi-Wans. If anyone has a junker they can spare pls let me know. (Shouldn't be too hard, this fig was junk right out of the box. Yeah, I went there. God, that figure is crap.)
A minor mod, I swapped the head and back-piece between the two versions of the figure, looks nice IMHO. Also came up with a new robot mode:
