I have a 30' 2004 Georgie Boy with the V10 and E4OD trans pulling a 24' Haulmark with all my junk and it does just fine. The Ford MH chassis is rated at 26000 GCWR, which is the MH and trailer combined weight. My MH, totally loaded, is less than 16,000 and the trailer and all the junk is right about 9K. Last time on the scales loaded with my "crew", fuel and water, it was right about 24K. The V10 does remarkably well. You'll just have to get used to the engine screaming at 4500 RPMs when it is really working hard but it will suprise you at how well it pulls.
You really have to pay attention to the hitch and what it is attached to. A lot depends on the wheelbase of the chassis on your box. If you have a short wheelbase then the OEM chassis gets extended by the coach mfg. This can be a recipe for disaster since a lot of times the material used for the extension is lighter weight than the OEM chassis and fabricated by some high school kid. Ultimately the hitch is connected to the chassis and if it is through weak frame extensions it is never going to be right.
When I went shopping for a box I searched until I found one that did not have any frame extensions and the hitch (Reese) was welded directly to the OEM chassis. I then had it reinforced further with some additional gussets. You MUST use a weight distribution hitch. I also added the dual-cam style sway bar. This setup is fairly expensive but it is worth it's weight in gold. The trailer is rock steady behind the MH and after a while you almost forget it's there. Look at a setup like this:
http://www.drawtite-hitches.com/prod...und_Bars,66078
I have never used a Trailer Toad but except for sway, it looks like it would be a nice setup too. It would certainly help keep the tongue weight to a minimum.
I fiddled with the placement of my car in the trailer to get the best tongue weight. I also added the Firestone air bags to the rear suspension which was a very noticable improvement too. They are cheap and really easy to install yourself on the Ford MH.
I have not had any trans problems although it doesn't suprise me to hear that others have. The E4OD/4R100 is essentially a C6 with an overdrive. It is a very stout unit and rated at 1000 ft/lbs of torque. It is the same trans they put behind the Powerstroke diesel for many years. Even so, I plan on adding a trans temp gauge and maybe a deep aluminum pan which adds six quarts. Heat is the trans killer and when the converter unlocks and your pulling a big hill, it's gonna get HOT.
Forget about gas mileage. I get 6 to 6.5 MPG when hauling the trailer. I have read a lot about the banks kit for the V10 and supposedly it really helps with pulling power, but does nothing for fuel mileage, which seems reasonable to me. You gotta burn fuel to make power. Pricey package though. I've been tempted, but haven't done it.
Watch those frame extensions..!!!!
Good luck