One of the more amazing things I've ever seen no guitar is when Rusty Cooley starts doing his 8 string sweeps on his 8 string... just insane...

I play GHS ZW's on all my guitars... I play both sets too... On my standard tuned strat I have the lighter ones... and I have the heavier ones on my other strat that is always tuned to drop D or lower... They get awesome tone.

I don't understand why you'd want 8 strings though... Just seems like a novelty more than a functional piece of equipment. But then again... I don't play any music that would require me to play any lower than drop D. or drop D half step down...