I'm doing almost the exact same thing with a remote control car I picked up at a yard sale for $2 and the same sort of spider you're using - one of those soft posables you find at Walmart for like $3. I decided to ditch the car body and just use the remote control chassis. I added loops of rebar tie wire in the bolt holes for mounting the spider. The trick with the spider car really is patience and waiting for the right time to spring it. As it stands this year, it is the cheapest prop I've made, at a grand total of about $6.
Next year, I'll be adding a spare battery pack and 8 red LED eyes to the spider to give it a little extra oomph. I might add a relay switch as well, so the eyes only light up when it moves. I'd love to gut the spider and add a mechanism to move the legs as well. I'll also build a second one for next year, since I still have a few more of those cheap remote control cars left that operate on another frequency. LOL. Can you imagine the reaction of 4or 5 of those things suddenly came at you?
Next year, I'll be adding a spare battery pack and 8 red LED eyes to the spider to give it a little extra oomph. I might add a relay switch as well, so the eyes only light up when it moves. I'd love to gut the spider and add a mechanism to move the legs as well. I'll also build a second one for next year, since I still have a few more of those cheap remote control cars left that operate on another frequency. LOL. Can you imagine the reaction of 4or 5 of those things suddenly came at you?