I am in the process of doing a 2/3 or 2/4 drop on the Yukon, still undecided. Really don't want to cut into anything so wondering if the travel mod is necessary? I've heard that with a 3" drop it's not needed but a 4" drop it's almost required? I have the shorter Belltech bump-stops as well as Air-Ride with the Max-Trailering. Also curious from people that have done it if 4" is to much when you still plan on hauling stuff a lot.
It depends on a few factors: The driving you do, loaded or not, towing or not and how unlevel your roads are and how fast you drive on them. Some people can do a 4" drop but drive on smooth roads and never tow or carry loads. So, even though the axle might be really close to the bump stop, it never hits or hits very gently due to their driving situations. On the other hand, someone with a 4" drop that hoons their car over curbs at roundabouts while carrying a loaded 100-quart ice chest and chubby passengers would be 100% sure to bottom out and would need to do as much clearancing as possible.
If it doesn't bottom out or not hard or frequently enough to bother you, then don't do the FTM if you don't want to. If it frequently bottoms out on the Belltech stops, then you'll have to proceed accordingly with reducing the amount of drop, trimming the BT bump stops down, replacing them with the stubby polyurethane ones or just doing the FTM and gaining back all your uptravel.
Mine is a little more than 4" and it carries and tows all I need it to. Granted, I'm not towing a 30' bumper pull. But, I've towed a compact 4-door car on a dolly and ~1,000 lbs. on a utility trailer for almost 800 miles without issue. I had to delete my factory ALC (the "air ride") due to the 4" drop, but I have Air Lift air springs in the rear coils that perform the same function as the ALC.