Andre,
Any thoughts on having a ‘traditional’ stiff walled Marathon Plus 1.75 on the back and a 2.00 Big Apple on the front to act as a shock absorber (a bit like a hardtail MTB)?

George had a good idea, posting photos; one is worth a thousand Dan-words. Here is my setup...

I mated the receiver bike rack (A) with the tandem tray (B), both shown in the photos below.

The tandem tray replaced the inner set of wheel hoops used for a single bike. The hoops are adjustable and unbolt to slide off if desired. Swapping the rack back and forth between configurations takes about 10 minutes.

Prices have soared astronomically of late. I got by cheap roughly a decade ago, paying USD$159 new for the receiver rack and the tandem tray was a Cragislist (America's Gumtree) find, costing $20. U-bolts and fasteners added maybe $12, bringing the total to about $192.

Best, Dan.

This is a tangential response to your question, James and Sue, but may be helpful to you...

When it came time to transport my non-separable tandem, I purchased a receiver-type (i.e "American" rather than the Euro-type hook) hitch mount rack intended for two single bicycles -- the kind with padded, ratcheting hooks that secured the top tubes while the bikes sat upright with their wheels in trays.

I then purchased a Yakima tray intended for a rooftop rack, the kind where thr tray rides on square-stock steel tubing, ending in an upright and faux front axle with a quick-release. I attached this alongside the inner tray of the hitch rack with squared u-bolts, washers, and nylock nuts. The tandem -- sans front wheel -- was loaded with the rack upright folded down, then raised to secure the bike once the tandem's fork was fastened to the Yakima faux axle using a quick-release intended for such. It made for a really secure attachment, using the fork mount as well as the padded hook on the top tube. It helped it was all at a convenient height so almost no lifting was involved.

The tandem extended a bit beyond each side of my 2012 Ford Focus hatchback but was within the outline of the external sideview mirrors, so anywhere the car would fit, the tandem would also and I could "monitor" the outboard edges of the tandem rear tire and fork end in the side mirrors when parking to make sure I didn't snag them on anything. My tandem is about 8.5ft/2.6m long overall with both wheels mounted, considerably less with the front wheel removed; that was key to making it fit within the car's sideview mirror outline.

It worked very well and was an inexpensive solution that added versatility to the rack already intended for single-bikes. Most of all, it was secure and safe.

I made sure to triangulate the mounting with sturdy nylon straps and a vinyl-dipped hook over the hatchback opening to reduce dynamic loads on the hitch mount. The tandem weighs 46lbs outfitted as usual, so about the same as two singles. Due to an abundance of caution, I avoided the temptation to add a single bike when we carried the tandem. The 1in solid bar mount in the hitch receiver didn't look robust enough to safely carry more and I'm still scarred by the sight of a collapsed hitch-mount rack dragging two very expensive bikes along the pavement at highway speeds, the owner still driving happily with the car stereo cranked to 11, oblivious till I caught their eye with frantic waves of my hands and gestures of alarm. By the time he stopped, there wasn't much left to salvage.

Maybe something in my solution will help spark an idea. Be sure to check local width regulations. I did in advance and found no flags or cautions were needed to be legal but I expect that could vary by locale.

Best, Dan.

What was the line from the movie? -- "Who are those guys??"   

Absolutely fantastic, George, and I loved every turn of the wheel. Hamburger and fries was the perfect choice in great ambience with new friends. Really must do this again!

All the best and with a big smile, Dan