I started the Saybrook backdrop a few weeks ago but I'd only gone to the edge of the proscenium with masonite since I wouldn't be able to curve it as tight as I needed to. Following a tip from Joe Fugate, I used some scrap vinyl flooring material to extend my backdrop around the tight curves at the "west" (right) end of the Saybrook scene. You can follow my process through the photos below...
|And here it is with the mesh tape added.
Once I knew the left edge was secure, I spread more adhesive directly onto the wall and rolled it out to be sure it spread evenly.
Pro Tip: In a situation like this, consider a backerboard rather than applying the vinyl directly to the wall. As you can see, having the vinyl go around the moulding and dip back to the wall creates some unfortunate shadows. The 1" gain of space there isn't worth the shadows, IMO. Note also how I cut it to go into the "tunnel." That's as simple as wrapping a present - just mark your cut and cut with regular scissors.
I also put adhesive on the other wall and applied mesh tape to the right edge of the vinyl to help it feather into the wall. After this, it's just a matter of adding coats of vinyl spackle - sanding in between coats and feathering everything in - and we'll be ready to paint!
Next time you're planning a backdrop, you may want to consider adding some vinyl. Not only does it go around tighter corners much more easily than masonite, but that flexibility makes it ideal for coving corners.
That said, I wouldn't recommend using vinyl exclusively since it's way too flexible for general use, IMO. If you plan to paint it at all after installation, you'll find that you'll need to have it sufficiently supported - and that's a lot of extra work, considering that masonite is to a great extent self-supporting.
But it's another alternative to add to your backdrop options. In the right spot, vinyl is the perfect fit.