Wiggle wire makes holes in poly - Normal?

I installed one side of my greenhouse poly with wiggle wire and channel.  I got the wire, channel and 6 mil poly from the same supplier.  As I installed the wiggle wire (while tugging on the poly to keep it taught) I noticed that about every 10th wiggle would rub through the poly as it got into position.  If I was extra careful I could avoid it but it's hard with one hand on the poly and one on the wiggle wire while 18' in the air on a ladder.

Is this normal for wiggle wire installation?

Also, I was successful at getting the poly pretty taut.  When I snap it with my finger it drums a bit.  Is it possible to get poly too tight?  I wasn't really pulling crazy hard on it and I didn't pull any white stretch marks into the poly.