Hi and welcome
What version of Visas Marr are you planning ?
Always good with lots of research and to make try-outs before using the right fabric, so your off to a great start
Regarding the boots, as long as the stretch panels are on the inside of the boot, like around a zipper, I don´t think, that it will be a problem.
Regarding the frustations about not getting anywhere - think, that we have all been there, so you just have to give yourself one goal instead of 10 and take one step of a time. Good things take time
Where do you think a piece is missing from the sewing machine ?? try sew some fabric together with it and see, how it turns out, or put a pic up inhere - perhaps I can help out ?
Looking forward to follow this one