So how do you guys solve the sitting position problem with desk flight sim without using desk mounts like these?
Originally I made some stand alone stands out of some laptop stands from IKEA and then made my own mount plates for them. That worked fine when I had a Saitek X52 because that set up was light and had little resistance. When I moved to the TM stuff, it was just too heavy and the stands tipped or slid around the floor too easily. That is what got me to the VIRPIL mounts, but as I said when I bought them they were VIRPIL's first mount attempt and were much cheaper. And they do work. Nothing wrong with them; just bulky.
The other option is to buy lower or short sticks that are designed for desktop use and have lower bases. In the high end market, VKB and VIRPIL both make ones that are not as tall and therefore more usable from the desktop. You'll still likely want a chair you can raise a bit though. Throttles are usually not a problem on the desktop. Cheaper stick and throttle combos usually are fine on desktop too. Even mid range ones like the Logitech X56 would likely be fine for desktop use.
Some people (@sswilson for example) have modded arms of chairs to accept homemade mounts. This is a good option for lighter set ups, but does need a chair with the right type of arms.
That is why this this flight/space sim hobby gets so expensive! It keeps driving you to better and better gear that then wants more comfortable (and expensive) set ups!