Like I said, I didn't think it all the way through, but not all dogs climb or jump 5' fences. Personally, if I were to do it, I'd build it with 6' panels.
It was just an idea....or something to spark convo.

Me personally..... I HAVE TO HAVE A TOP on any pen of mine. I live by the proverbial, "If it CAN happen, it WILL happen"

Carry on!