I have a new NL 8'11" on my short bed truck and pulling a trailer requires about a 42" extension. TorkLift would be the method of choice for your application with the horse trailer, but it's expensive too just like the NL. Upgraded sway bars, StableLoads, shocks, airbags, etc. should help with the pucker factor you experienced earlier.
With respect to water infiltration on the fiberglass units, it still exists. Even on my new NL I check to make sure the caulking around any of the openings is good and intend to remedy any areas that aren't in real time when I find them. About two hours away from my house here in Ohio is a TC dealership that carries most of the major brands, so I had the opportunity to climb inside a number of units before making the easy decision to pay a little extra for the NL. They are expensive though, but I believe you get what you pay for.
Good luck