[D&D 3.x] Low-power level 8 party and module

[Avoraciopoctules]

Lately, my local RPG group is getting pretty scattered, and when we do get together, we usually don't advance the campaign we choose to play very far. Because of this, I am strongly considering ending/putting on hold most or all of my more open-ended games and switching to preplanned modules I can ideally finish in around 4 hours if I Magical Tea Party quite a bit, and at most 4 5-hour sessions if I avoid cutting around mechanics I find tiresome.

I'm planning a module for a party of 2-6 PCs of level 8, most of whom will be premade so as to stay at a particular power level. I want PCs that can't reliably pass a Same Game test with around 50% or more success, but can take on CR 4 or 5 monsters fairly reliably. One player has expressed an interest in playing a minotaur with 4 class levels and a tiefling Cerebromancer. This player has also indicated that he would like to face challenges involving managing limited resources, so he is unlikely to take or want a source of unlimited magical healing.

I'm thinking of CR 3-5 mooks, and something like a level 9 or 10 True Fiend or a Frost Giant built like a PC as a boss. If I go with a closet troll, I'm probably going to let the PCs have several opportunities to outmaneuver it. I want a believable and understandable bunch of antagonists, and there should be at least a couple of opportunities for the PCs to improve their situation or resolve conflict by talking things out.

So far, I'm thinking of a fairly straightforward mission (this is a Planescape game where the PCs are part of the same company of adventurers. I think I mentioned it later on in this thread: http://tgdmb.com/viewtopic.php?t=50175 ) focused on taking over a castle in snowy and rocky terrain. I've done these in the past and everyone seemed to have fun with them.

Inspiration for the setting of the module was taken from this picture. I have no idea where it is from:
http://i244.photobucket.com/albums/gg21 ... itadel.jpg

As things stand, I'm just in the brainstorming phase. Any thoughts or suggestions for any aspects of this? I'm open to using any 3.x or Tome content, but I prefer things I can built in PCGen without having to write in new content too much.

[Avoraciopoctules]

I'm thinking of something like the following for premade PC options, since they won't require too much difficulty to make and seem to be around the power level that feels ideal for the challenge of the planned adventure:

Archivist 4 / Tome Knight 4
Tome Fighter 4 / Tome Warmage 4
Assassin 4 / Spherelock (eldritch blast 4d6 since it scales by class level) 4
Tome Fighter 4 / Curator 4

For basic enemies, I'm considering batches of level 4 Tome Adepts (maybe with a positive energy healing option for their elemental attack) and Warriors, with level 6 SRD Fighters that have access to maneuvers and level 4 Tome Warmages as group commanders. I may minimize the HP rolls of some of the mooks.

If I use a Snowscaper ( http://www.tgdmb.com/viewtopic.php?t=50012 ) as an enemy, what level would make it a challenge, but unlikely to kill off anyone?
EDIT: I should say, unlikely to kill anyone if the group is played reasonably intelligently.

[Avoraciopoctules]

Decided that I'm definitely not going to worry about XP or treasure packages all that much. The PCs start with all 8 of their Minor Magic Items, and there's not going to be any leveling up in the adventure. This should save me a fair amount of bookkeeping time.