I'd add that it also depends how many rabbits you are expecting to hit the nets. If you think you're in for a bumper bag, then go less distance between poles. Sod's law you'll space them at 6yds+ thinking you won't do any good, you'll bant the field, get back to your net and find it pulled down with trapped rabbits, but still have bunnies winging over the top at the last minute. Now that's annoying!
If in doubt, set too many poles rather than too few.
mmmm, might try a drop later.....