First let me welcome you to FTE and the 6.2 forum.
Sounds like a nice boat your pulling around and a good load to test your 6.2. If you want to get a little better mileage try using the manual mode instead of the tow haul, the TH is real aggressive when it comes to down shifts when its really isn't needed. If you scroll through your message center it will tell you to turn TH off when it isn't needed but turn it back on if road conditions cause the transmission to hunt.
Moderator 6.2 & V10 Forum
2013 F350 Lariat SC DRW 2WD 6.2 4.30 Gears Air Lifts 50 Aux tank
2003 F150 SC XLT 4x4 4.6L 3.55 gears
2003 HH Premier 35 FKTG