Sorry. I got no engine nearby (and by that I mean I have no computer available on which I can run it or which has a good enough internet connection to download it within the next few days) and never worked with mesh generation so far so I don’t know where your code goes wrong.
Have you tried placing it manually into the spot (simulate and then change the location and rotation) to see if it has the correct size. Maybe your mesh component is a bit off or the generator only generates a mesh but not with the exact location (after all you only provide a triangle and not the locations anymore).
Just random guesses though. As I said. I never worked with this so far.
Cheers