Hi Darren,
I haven't used it - but a fox will go over the top of a 6ft fence (I say this having lost 4 ducks that were behind a 6ft fence a month ago and were killed by a fox...).
If it is electrified, you will probably be ok - the key here is that there is a strand at low level to stop digging, and higher up to stop climbing. It doesn't need to be so high then.
Hope this gives you some ideas. Tim.