I don't have regular field fence but it seems 4-5ft is extreme. Most are rated for 8ft space and high tensile is 16.
We did cattle panels last year for our first pen. Wasn't too large but plenty big with tons of bushy graze for them to munch. We were utilizing some posts that were already in behind the barn. The posts were around 16 ft apart but didn't always add up so there were spots I had to wire the two ends of the panels together. I thought for sure it wouldn't hold them from all the horror stories I'd heard/read. They never got out of there but they always had food and water etc.. so never felt the need to escape.
This year, we did one of the two acre Pasture/treeline and used the high tensile field fence with the 16 ft posts that were there. So far it's keeping the goats, IPPs, and Shetland pony all safely inside. I think some goats are just more prone to escaping and some are content as long as they get care and daily attention.
When I lived in CT, the farm I worked on had huge Nubians and had a small pen with fence they easily could have jumped but they never got out.
I'd suggest starting with a smaller penned area so you can figure out their personalities and your own management style before dumping a ton on something that might not be right for your place..just my thoughts though.
