The original box set, Ruins of Undermountain, had 124 developed rooms or areas of interest. It breaks down like this:
Level 1 = 42 core rooms/28 areas of interest = 70 total
Level 2 = 17 core rooms/26 areas of interest = 43 total
Level 3 = 11 core rooms/0 areas of interest = 11 total
Grand total: 124
So far, for Ruins of Undermountain III: The Deadly Levels, we have:
Level 7 = 41 core rooms/26 areas of interest = 67 total
Level 8 = 41 core rooms/26 areas of interest = 67 total
Sub-level = ? core rooms/? areas of interest = ? total
Grand total: 134 plus however many we include on the sub-level.
A sub-level should have fewer rooms than a main level. In RoU, they had no areas of interest on the Level 3. If we follow that (ie no areas of interest on the sub-level), we can put 16 rooms on the sub-level for a grand total of 150 developed rooms. A nice clean number. Or if we keep the 26 areas of interest consistent (which I'm definitely doing for all the main levels...Levels 7, 8, 9, and also Levels 4, 5, and 6 when we do RoUIV and re-do RoUII), that comes to 160 rooms/areas plus however many core rooms we do. If we do 25 core rooms for the sub-level plus the 26 areas of interest, we top out at 185 developed rooms. Wow!

I posed the question to the development team, but I wanted a public discussion on it as well. For purposes of discussion, keep the following in mind...
1. For all RoU BIP releases, all main levels of Undermountain (Levels 4,5,6,7,8, and 9) will have exactly 26 areas of interest each, plus whatever number of core rooms we decide on.
2. I don't care if sub-levels have areas of interest and frankly I prefer they don't. I hate doing areas of interest because they are just as much work as normal core rooms.
3. Each Undermountain project at BIP will closely follow Ruins of Undermountain (the original) as a guide, hence we must have at least 124 developed rooms in each release...RoUIII, RoUIV, and RoUII (the remake). If people want only 124 rooms. I don't mind doing more, but I won't do less.
4. Keep in mind that I am trying to work on one of the most common complaints I hear from people who criticize Undermountain...that the original set came with far too many empty, undeveloped rooms. I'm trying to strike a better ratio where there are lots of developed rooms, and plenty of room for DMs to expand, but not so much room to expand that the map looks empty. For example, Level 3 in RoU is a double-sized levels (two full sized posters) and yet it has just 11 developed areas. I'd rather have plenty of developed rooms on any level or sub-level we make, so that it looks developed.
So, comments, suggestions, etc?