Looking really awesome so far. For a jumping spider. I would lean toward wire for the legs. Depending on the motion, they may take a lot of abuse.
I built a jumping spider a couple years ago. It is a great prop. I used a spider from Unit-70. You will save a ton making your own and it looks really good!
Yep it will be pneumatic...the plan is a plexi-glass containment tank with blinking security LEDs. The spider jumpsslightly 3 or 4 times at a lower height, then one big jump (the lid opens)...LEDs go off...warning light and maybe a (containment breached sound track....warning...warning...all safety doors have been activated...BOOM...BOOOM (doors shutting)....Have a nice day)