Thanks SO MUCH to popup for answering and pitching in. Note: popup's layouts are amazing (JD-990, Korg EX8000, Casio XW revamp).
Anyway, @orpheus: regarding selling of layouts, it's fine, but there's no way to do this in the App, and we don't provide support for that. Also, at least right now (Nov 2013) I can tell you that it would be very hard to make any serious money selling layouts, even if we did have a setup for this. (please note that some of the other apps, including MIDI Controller Pro, offer to BUY layouts from users... we don't work like this, but it might be another avenue to consider. We have NOT tried that out nor have we really tested their app).
Regarding one-big-page: it's possible to stretch controls from left to right across the break (but not from right to left, so you have to be aware of this).
Good luck with MIDI Designer and please feel free to ask questions here. It's much better, for the site and for future users, if each of your questions/suggestions contains one concern.
Thanks for checking out MIDI Designer and best of luck!