I did solve my problem finally, with your help, but I wasn't able to get "loft" to work that way for me. I ended up drawing rectangles over the open areas, using "planar" to make them surfaces, and then "union" to use them to seal up the holes. I could then cut the new holes using "diff".

BTW, the part looks great now but I wonder if the database for it is a mess because of all the operations that I've had to go through to get where I'm finally at.

Thanks,
Mark