Just came across your post. I just replaced 2 of my original non-opening ports with 2 new opening ones and re-placed the acrylic in 2 others due to money matters. I was also a bit intiminated by my lack of experience in doing the job. See my post in gear and maintenence. My openings were a bit shy of 6" x 24", hence the need to route the openings. The end result looks great, doesn't leak (yet). I shoulda done all 4 windows. next winter for the other 2. I can give you the source for these windows.