I'm a little late to the party so bare with me...So our rear travel is just shy of 14" which means by my estimate we have about 7" of compression travel from normal stock ride height (again my estimate, for those who have measured and have the real numbers please chime in..thanks) which means with a 3" travel bump kit there are 4" before you're into the the bump....So if you add a 3" extension you are now only 1" from hitting the extended bump...You now add your trailer and for the first inch it's same as stock, but as you lower the trailer you start getting into the bump...how far in depends of course on the weight and the pressure in the bump stop...so say for simple math your trailer drops the rear end 2" normally, but with the extensions it now only drops 1.5"...Some guys will still complain as they want zero drop or maybe an inch max..BUT for this example our guy can live with the 1.5" over the 2.0".
Now here is where it's get interesting...You have now used .5" of bump travel, meaning you only have 2.5" of compression travel left...how is that going to work as you hit even medium size bumps in the road and still ride extremely stiff as you use most of the bump travel?
If you left it all alone with no extensions you would drop 2.0" but still have 5" of compression travel, and 2" before you're even into the bumps which have 3" more travel...
All which means a much smoother ride and still plenty of wheel travel to handle the road conditions...Remember a stock F150 won't have 5" of compression travel after squatting 2"...
The above example is EXACTLY what my last pre-runner (2004 Titan 2wd with a Deaver mini pak and Light Racing 3" travel bump kit) truck had in the rear. I towed a 4500-4700lb enclosed trailer to Las Vegas and yes it squatted 2" in the rear...so what!...it handled and yes steered just fine AND the rear suspension ate everything on the I-15 awesomely!
Sorry long story:
At the time of this tow, they were doing repairs to the I-15 by cutting across all 4 lanes for about 40-60ft with a 2"+ sharp drop off and "curbs" when coming out of these cuts...there were all sorts of yellow slow down signs warning of sharp drop offs and such with 50 mph suggested speed limit...I never slowed down, hit the drop offs and "curbs" on the other side at 62 mph and laughed as the rear end soaked this all up smooth as silk...I really mean it I hit the other side and the rear end just soaked it.
But here is the real story...When I pulled into the pits and parked with 5 other trucks with their trailers in our saved area all the guys ran up to me to inspect the trailer and they then informed me that 3 of the 5 trailers had bent tongues from bottoming out so hard on the cut out on the I-15. They asked how the truck felt when hitting ruts and I told them I really never felt them and there was ZERO damage to the trailer I was pulling!
I would agree this may be an extreme example, but the theory is still sound...wheel travel saves the truck and trailer if you hit anything...
Again sorry for the long post...
