Air bags do a good job of disengaging the stiff part of your leaf spring pack from the load and softening up the rear, which is what you don't want. Take 'er easy there.
The solution has several parts:
1. Weigh trailer and tongue in the various configurations you tow. Typically that's with and without a toy in back.
2. Make sure both configurations have tongue weight at least 10% of trailer weight.
3. Install an Equal-I-zer hitch (accept no substitutes)
4. Working on level ground and reading the equalizer instructions, determine the setting heights for the equalizer hanger arms on your trailer. It's likely that you need to set them at one height for no toy, another for another toy.
I to a ~11k boat trailer with a SRW F350. I made an adaptor for the trailer tongue which lets me use the equalizer (I also have elec/hyd brakes, no surge). That setup is awesome.
