Chris, its a tricky one with RE to the up-trace when paternostering for Perch. With pike yes everytime but on a Perch rig the up-trace looks just to blatant to me and i avoid it,ive had no problems yet, but you've got me thinking. If your worried about pike rolling up the trace, maybe cover the wire with rig tubing? Or try a slightly different presentation, if you want the bait tethered go for the CD rig or try a free-rover.
Dave, ive looked at quicksilver in the tackle shop and decided against using it for Perch again it just looks to blatant with its waxy and springy feel. Its each to there own and you seem to do well on it but i would urge caution about not using wire for eels and especially zander. Zanders teeth demand the use of wire and you are definatly likely to encounter Pike whilst zander fishing so why take the risk. Not only is it dodgy for the pike but for the sake of using a wire trace you could end up loosing the pike of a lifetime, is it worth it?
Same for eels. Its a long running debate amongst eel anglers, quicksilver or wire?It all depends on the type of eel in your venue, if they are the small mouthed invertibrate feeders you could get away with it, the broadheaded fish eating eels will make mincemeat out of it. The trouble is you are likely to encounter both varietys of eel in the same water so id cover both bases and use wire. Even wire is not totally fool proof as big eels in rare/extreme circumstances have been known to cut through wire with thier violent headshaking acting almost like a hacksaw.
Most of the best eel anglers use wire so its a no brainer really.