[Astroboy]

With that much weight plus the leveraging effect of the extension, you're definitely pushing the envelop. Saying I wouldn't be confortable is an understatement.

FYI, you can find on the net, many instances of GM hitches failing and ripped off (many Suburbans and Tahoes).

The OEM hitch has a sticker that indicates the rating of 600 lb tongue weight without WD or 1000 lb tongue weight with WD.

The hitch hangs on the main ladder frame via clamps that is merely a few inches wide.

Solution -> Upgrade your hitch to class IV.

For a few hundred bucks, you can easily have a local hitch shop weld some additional cross members and reinforce the hitch. They can also legally rebadge and give it new rating.

I had this done, and now my new sticker says the hitch is good to tow up to 10,000 lb trailer and 1200 lb tongue weight without WD.