Putting a fence on a poured-concrete yard on a slope

[jamiek]

Hi

I'm looking for some advice. I;ve got a poured conrete drive. My wife wants a fence down the middle of the drive we share with the neighbours so I was thinking of getting those post bases to hold wooden fence posts - and then hang the fence panels on them. Obviously we want the fence posts to be plumb... so I was thinking of using washers to ge the post bases level - so my question is how much of a slope is too much of a slope? As in, is my drive too steep for this? It's not a steep slope - it was poured concrete.

thanks in advance for any advice or tips!
Cheers!