Hi fnappy,
Welcome to the Mattress Forum! 
I’m happy that the information presented here has been useful to you.
As you’re considering the DIY route for a mattress, and just in case you haven’t read it yet, I would start is by reading option 3 in post #15 here and the posts it links to (and option #1 and #2 as well) so that you have more realistic expectations and that you are comfortable with the learning curve, uncertainty, trial and error, or in some cases the higher costs that may be involved in the DIY process. While it can certainly be a rewarding project … the best approach to a DIY mattress is a “spirit of adventure” where what you learn and the satisfaction that comes from the process itself is more important than any cost savings you may realize (which may or may not happen).
If you have more specific questions as you go through the process, I’ll do my best to be assistive.
Phoenix