There was a thread about a year or so ago about tire pressures for Georgetowns - do a search and you will find it.
It is important to know the weight of your rig - also weigh the corners - and it sounds like you will get around to weighing.
I too have 19.5s on my Georgetown and I run my tires at 90-91 PSI.
Bubba & Chiquita + Two Vizslas (Barley and Sophie)
2008 Georgetown 315DS SE LTD
2011 Jeep Wrangler Unlimited Rubicon
Sterling All-Terrain Tow Bar - SMI Stay-In-Play Duo
Do What You Like - Like What You Do!