PropellerHead, nice X5 (blue is best, IMO, hahaha). I'm concerned about excess loading and the resultant tire & suspension wear that your extended bike carrier may end up causing.
Are your bikes very heavy, do you have air springs to help compensate for the added load, and have you considered using a small trailer (either an enclosed or an open type) that would help distribute the rear load better?
I used to have a single-motorcycle trailer that the previous owner had converted to haul three bicycles; it was 50" wide X 60" long (with a 36" tongue, IIRC), and it would've been perfect for your bikes, but I converted it to a 4'x8' squareback camping trailer.
"single-bed" frame used for size comparison
In your case, with the aluminum carrier sticking way out behind the truck, the carrier/bikes exert a greater load on the rear axle, tires, and suspension than if you were towing a small trailer (like shown in another of your photos).
see how the trailer helps ditribute the load
I carry a lot of tools and supplies in the trunk of my X5, pushing them up against the rear seat back, to focus the weight closer to the rear axle centerline. I have steel springs, not air suspension, but if I were to try to carry your bike carrier, I'd have to add supplementary overload springs (possibly Sumo or Timbren or homemade, like on my camping trailer), air shocks (if available for X5's), or overload shocks (coil over shock), like I use on my 2500HD Chevy.
comparison of loading
Though I don't carry bikes like you, I do haul my 2225 lb camping trailer, which exerts 245 lbs on the hitch (negligible behind the overbuilt 2500HD, but perhaps a concern behind the X5, if/when I install an AHM braking module or alternative). I sometimes use a "Weight Distributing Hitch" (if camping far away or semi-offroad, or hauling heavier trailers (up to 11000 lbs, max), and would do the same behind the X5, because I can really tell the difference when the WDH is being used.
I'm just sharing my opinion and some experience with you, not being critical. Perhaps at some later date you might need to switch to a light trailer, and if so, could you compare the differences with me/us?