Double receiver hitch for tow dolly and bike rack?

I liked this solution on my previous coach. I had a hitch shop weld a second receiver above the stock receiver. My brother-in-law had the same issue, but needed one below his. He had the same thing done. It gives you that extra receiver without having to add cumbersome extra hitches that extend your tow vehicles.

I tow four down rather than a dolly and used a Dual Hitch Receiver. It has a higher weight rating than my hitch and tow bar so a bit of overkill and might be a bit outside of your budget. I needed the drop to line up the tow bar to the car base plate. Worked great for 10,000 miles towing with a bike rack. Changed from a Accord to a CRV with so I no long need the drop and the bike rack is now on the back of the CRV. I did cut back the rack a bit so it was closer to the coach to clear the vertical pivot point of the tow bar.

Same hitch at harbor freight is $30.00
http://www.harborfreight.com/dual-hitch-extender-69881.html

I use this when we are towing our car and hauling bikes, Just make sure you have clearance between bikes and tow vehicle and you should be fine.As far as towing heavy vehicles... I dont believe it matters as there is virtually no weight on hitch as the dolly cradle supports the weight of vehicle

Any extension sacrifice safety and load carrying.
You did realize it is 4000 lb rated while I see pretty heavy vehicles in your profile?
I've been carrying 450 lb PWC on the rear of my motorhomes, but always had 3 receivers welded. Any bike rack on single receiver will bounce a lot.