Need Advice on Changing Lift Bars

I just put a pair of G3 Targa bindings on a new set of tele skis (new Atomic Tacoras for only $220!... ). Rather than buying a new set of lift bars, I was hoping to take them off my old set of skis. My old skis have G3 shims. I'm having trouble getting the rear shim off because the screws have what appears to be plastic caps over them and try as I might, I can't seem to get them to come off. Anyone have any advice on how to get these caps off so I can unscrew the shim and get my lift bar off?

Thanks!

I'm pretty sure G3 recommends driving a small screw into the plug to give you something to grab ahold of. I'm going to have to do this myself if I can find some climbing bars.