As an author who publishes his own books, I tried a new approach with my latest novel. Instead of the standard manuscript format, I typed my book directly into a document formatted for paperback printing. There are several advantages to this approach. One is that you can see what the book will look like as you go. Another advantage is that when you're done the book is finished and there are no surprises related to layout.
I still printed it out a few times during the writing process, and made handwritten edits. The fact that it wasn't double-spaced didn't hinder the effort since the margins were extra-large. The book size I use is 5.25 in. by 8 in.
One problem I had was when I sent the near-complete book to an editor. For some reason the first thing she did was change the format to the standard layout for a manuscript. I'm not sure if she did that for printing or not. It wasn't a major problem since I easily got it back into the publishing format when she was finished. Just seemed like an unnecessary step to me.
The only real problem I had was when I got ready to print a proof copy. I uploaded the text to CreateSpace and was told it was the wrong size. I was given a couple of options to continue, neither were what I wanted, but I went ahead since the initial five books were for beta readers only.
I scoffed when CreateSpace said I wouldn't have had the problem if I had used the Microsoft Word templates they provide—because I had used their templates. But, after checking closer, it turns out I had used the wrong one. After changing to the correct template, the book was longer (in pages) and looked more like what I had in mind.
See https://www.createspace.com/en/community/docs/DOC-1323 to get a template.
Let me know what you think of this approach.