ive recorded all of my tests and their results in this video, along with a better explanation of the proof-of-concept coroplast plate I attached to my dropper hitch.Alrighty,
I'm uploading a video to youtube that documents all of my testing and my little DIY fixes, but Ill go ahead and summarize here:
the RAB system is able to tell if there is a bulky object (a.k.a trailer) right behind the center of the vehicle, but it's not very good at it, and needs some help. if you have a trailer with a lot of bulky stuff on the tongue (like a motorized jack or propane tanks) the Ascent will "see" it and disable RAB. same goes for a lot of the chunkier Bike racks out there. if you have something small or thin hooked up to the ascent, or you're using a hitch with a big drop, the RAB sensors won't "see" it right behind the vehicle, only the body of the trailer further back, which RAB will then treat like an obstacle and will intervene.
this explains why RVers and other "bulky trailer" towing folks haven't had this issue, whereas anyone pulling a boat trailer or a utility trailer probably has.
Supposedly, if the vehicle sags (detects a "change in ground clearance", per the owners manual) enough due to load, It will auto-disable RAB for that reason alone, but not everyone is pulls a 4,990-lb trailer with a 499-lb tongue weight, so this information isnt practical as far as disabling RAB by default for Everyone's trailering needs...
now for solutions:
step 1. go into your i/Set menu in the gauge cluster with the ascent in PARK. page 5/9 is for RAB settings, go down to disable the sonar beeping noise thing. exit.
step 2. you've got options:
-if you slap some cardboard on the tongue of your trailer or on your hitch itself, (provided the piece is big enough) RAB will pick it up, and auto-disable. you can do this just to your hitch even without a trailer connected with minimal tongue weight. I cut out a 12x18" piece of Coroplast and zip-tied it to my dropper hitch. works like a charm. makes the most sense to me if you have more than one trailer, even if you also need to do this mod to multiple hitches.
-if you're really desperate, or just hate RAB in its entirety, you can tape over the RAB sensors on the bumper, leaving a little bit of air gap between the tape and each sensor, and RAB will think it is mud or snow and auto-disable, as its stated in the owners manual. Woo, duct tape on a $35-45k car...
-if you are looking to add any accessories to your trailer (spare tire carrier, electric jack, propane, battery, toolbox, etc...) consider SAFELY adding that item really close to the front of your trailer (based on my testing it should be no further than 17" away from the bumper of your ascent to be considered a "trailer" by the RAB system) if you only have one trailer, this probably makes the most sense.
I would suspect if there's any sort of mid-cycle refresh coming, they're going to toss in that 12 inch screen, which, for all of its flaws, does have the option to permanently disable RAB in the Outback/Legacy, but idk if that would also require an updated BCM or ABS module.
looking forward to the community improving on my methods and conclusions so we can all learn something!