I use the same set up (I have a 30" inside leg)
I used the standard GSA seat for a year which was fine, if a little tall, up to a 150 miles then the pain started, so I used an airhawk as well, which extended the pain range by another couple of hundred miles, but left me on the tips of my toes.
When I changed to the GS low seat, I thought I would suffer more due to the lack of padding, but reasoned I could use the airhawk on trips. The exact opposite happened the low seat is very comfortable up to a tankfull (300 ish miles) i would still use the airhawk on real long trips but its nowhere near the "essential" item I thought it would be
Shep