I think you need to look closely at the design of the frame - at least if you want to build a conventional teardrop. Lots of pop-up frames pictured here have their wheels
inside the frame, so there is nothing sensible you can do to narrow the frame to the width of a teardrop. No problem if you want a 80" wide teardrop, but in many cases it would be easier to start again on a new frame than be able to narrow it to 60" or less.
Here's an example:

- primer2.jpg (59.92 KiB) Viewed 355 times