I found this thread interesting, and came up with an alternative that has worked well for me: vellum sheets. I use the 29-pound version, which I find a bit thick. I've used it for several days, and a sheet lasts me at least several times. In fact, there are barely indentations on it after repeated uses. 

Considering that traditional vellum is parchment made from calfskin I would assume he using a modern product by that name! Using animal vellum for typewriter backings sheets is is something like putting gold leaf on ice cream. Which people have done!

I had a problem with furnace exhaust leaking into the basement so I put a fan in the window to exhaust it. It took a boiler tech to illustrate to me that understanding a principle is not the same as applying it to reality, when he pointed out that the exhaust fan was lowering air pressure in the basement and sucking more exhaust gas out, making the problem worse. Backing sheets are something like that since if the problem is that the type is being stopped by a hard platen and cutting the paper then raising the typing surface means the anvil has even less roll and even more of the impact of stopping the action is being absorbed by the type. Does not mean they should not be used but something to be aware of. 

I have typewriters with hard platens that hardly need a backing sheet and do not punch through paper - because the type bars are stopped mainly by the anvil and not the paper. A 1926 Remington and a 1929 LC Smith do not have much problem using both sides of a sheet of paper while many later machines make the back of the paper look like a sheet of braille.  A deliberate decision to use the platen to allow looser manufacturing tolerances? 

I don't recall if this issue has been addressed.  While the main concern is using backing sheets to prevent punching holes in the paper in the process of typing, I have another concern to go along with this:  Using backing sheets to cut down on the wear and tear of the typebar slugs.  Constantly hitting a hard platen I would think would have a wearing effect on the typefaces--especially on letters most commonly used such as the letter e.  Yes, I have machines that span the ages of about 55 to 105, and yes, though the platens are smooth, they are also hardened with age.  To get all these recovered would take the amount of the National Debt to get done, if I were to take proper channels.  But since I can't afford a flea a wrestling jacket just now, I use two sheets of regular paper along with the one I intend to transmit print upon, and I am working on being more ginger with the keys--kind of like driving a car being careful with the gas pedal to save fuel.