If your truck were a 13 it would be 2" lower in the rear.

 

Seems to me that you are caring way to much about how your "work" truck looks like when it's towing. While adding some leaf springs might make your truck handle better loaded, I think it's negligible the difference it adds between the stock F350 springs. I would agree with you if you were talking about towing your 5th wheel, but your talking about towing a 20' trailer that has two mowers on it(assuming zero turns). Glad you got your truck fixed how you want it, so lets see some pictures now!

 

I'll get some pics soon.

As for the sag, how it looks is a minor concern. The uneven tire wear, headlights blinding other drivers at night, etc. is what was an issue. My truck has a trailer behind it 95% of the time its on the road. How it drives with a trailer is 20 times more important than how it drives without.

 

I haven't looked at the spring packs on the newer trucks. On my 04 F250 I made a very cheap but very effective mod. I took my overload springs out and turned them over. The overloads on the 04 turned down so the suspension had to be almost totally compressed to get any help from the overloads, with them turned over/up the suspension only had to sag an inch and a half or so and the overloads were in play. It never changed the ride of the truck, cost me half an hour of time, and made my truck handle larger loads with much less sag.

 

Maybe I just don't see it in the new ones but I liked when the trucks had a little bit more rise in the rear before it was loaded. That way when loaded it sat level. Or when REALLY loaded it was finally sitting lower than level. It seems more trucks come closer to level and end up nose up when loaded. Even the 250's with the shorter blocks almost look rear down to start....

 

Uneven tire wear? On the rear?

 

Hey, this guy is pretty smart.

 

I recently bought an '11 F250 'assuming' it would not tail drag with our 5er hooked on - much like my '06 F350 which dropped maybe an inch with that load and never to the overloads. $331 later a set of Firestone Ride Rites made that happen. I also have a set of 1224 pound add-a-leafs from General Spring that I'll be installing shortly then use the air bags just for stability while pulling the trailer. I don't have the on board compressor but so far they have maintained 20 pounds for 3-4 weeks plus the ride - it's riding/handling like a 'real' Super Duty now instead of a marshmallow Lincoln.

 

I had the spring shop install a extra spring on mine too. When I was towing my TT with the golf cart in the bed the springs were all the way compressed. With the extra leaf it handles much better, but mine in a F250 too. Plus this was way cheaper then the airbags, since I wanted everything auto if I would have gotten them.