Ok, so we're not doing Level 4 right now.Levels 1-3 are detailed (obviously) in the original box set, and in there it spells out that Level 4 is a farm level, that the "mid levels below that" are dominated by Halaster's apprentices (hence, Levels 5-7 should be the levels of Trobriand, Muiral, and Arcturia), that directly below those levels is a twisted area of confusing sub-levels called "The Dark Levels", that below those Dark Levels is an area dominated by oozes, slimes, jellies, etc (ie Level 8 ). Then they list the final main level as Halaster's Lair ("The Mad Wizard's Lair"), ie Level 9.
What needed to be done with Ruins of Undermountain II (aside from hiring me to do the damned thing correctly!) was to have Greenwood write it (not the hacks they hired!), and to detail Level 4: The Farm Levels, Level 5: Trobriand's Graveyard, and one or two of the sub-levels from the Dark Levels.
Then Ruins of Undermountain III would have detailed Level 6: Muiral's Gauntlet, Level 7: Arcturia's Abode, and Level 8: The Slime Level.
Finally, Ruins of Undermountain IV would detail Level 9: Halaster's Lair, which would be a quadruple-sized layer (ie four maps for that one layer) that would warrant its own box set. Or perhaps a triple sized layer and some of the Realms Below areas that link to Undermountain. Eh. I think that would be anti-climactic. I'd stick with a huge Level 9 for Halaster.
I'd have followed this pattern for the BIP Project, but I didn't feel like detailing a massive farm, mainly because I couldn't tap my creativity as I wasn't inspired by a big-ass underground farm.
Ruins of Undermountain III: The Deadly Levels is going to cover Level 7: Arcturia's Abode (since she's the last apprentice listed in the original box set that hasn't been given a level as yet), Level 8: The Slime Level (since that's the next main level) and two sub-levels (to round it out and provide 4 full maps as the original box set did*).
Level 7 has 40 developed core rooms and 14 areas of interest for a total of 54 developed rooms/areas. Level 8 has 32 developed core rooms and 16 areas of interest for a total of 48 developed rooms/areas. That comes to 102 developed rooms/areas.
I'm considering making the two sub-levels smaller, perhaps small enough so that both can fit on one map. Not every level and sub-level has to be a full sized map, and most of them in RoUII were no more than wasted space anyway. Plus, a sub-level by definition should be a bit smaller than a full level. So I'm thinking 12 developed rooms on one level and 10 on the other sub-level, which should work, considering they'll be half the size. That means we'll have a total of 124 developed rooms, the same as the original box set!

The only problem I see with that is we'll only have 3 full sized maps in total...one for Level 7, one for Level 8, and one that shows two different sub-levels on the same side (one up top, one on the bottom). The box sets usually have 4 maps. Does anyone else here think that matters, or should we make the sub-levels full-sized maps? So far, only 5 of the 14 originally mentioned sub-levels have been developed (The Lost Level, Maddgoth's Castle, Crystal Labyrinth/Stardock, Wyllowwood, Adventures - these are the individual modules and what was added to RoUII). That leaves 9 free ones, but I don't want to over-develop Undermountain.
I was thinking of doing 3 sub-levels (one a full sized map, the other two share one full sized map) so that we can have a 4th map, but I wonder if that's overkill?
What do the rest of you think? Is it important to have 4 full sized maps, or should the quality make up for the lack of one map?
Finally, I'm thinking ahead to Level 9: Lair of the Mad Mage (Halaster's Level). It has to be at least a double-sized level. But unlike Level 3, I think it'd be better joined side-by-side, not top-to-bottom. However, I'm considering a triple sized map or even a quadruple sized map. It is, after all, the most lethal, most challenging, ultimate gauntlet layer in all of Undermountain!

How big do you guys think it should be? Double sized? Triple? Quadruple?
I planned on having that one level by itself be the entire project for Ruins of Undermountain IV: Lair of the Mad Mage. Why have any sub-levels? It's anti-climactic I think. But with just a double-sized map, that means if I develop say 50 rooms, that's all that the reader gets, because we need to leave plenty of space for the various fans and DMs to customize. And that's less than half a box set (they should be around 125 rooms). With a quadruple sized map, I can develop 125-150 rooms and it would be the same number of rooms developed in the original box set, plus the same ratio of developed to undeveloped rooms. That is quite a lot of mapping though!

Well, thoughts, ideas, suggestions?