Ken, what about looking into having something custom made to zip onto your existing RTT that could offer a larger ground level tent. There must be someone on the front range capable of making something. Awning maker? or such. Or make something to bridge the Oz tent if you go that route.
Speski OffRoad LTD, Cargo Solutions for Toyota 4x4's http://www.SpeskiOffRoad.com
"80 series, with a fridge"
1976 FJ40, Project with little progress.
2004 Starcraft 10RT