I have solved the problems with version 3. I found an old but larger desktop. It was large enough that I could move the monitor arm mount from the window sill to the board which also added to stability. To add further stability I added two cement blocks. The cement also add a decidedly manly feel. I decided to leave the dirt from the yard on them for aesthetic purposes. There is now a significant overhang from the old desk so I can sit comfortable and ergonomically when I finally need to sit down.