[3.5e] Gesalt Campaign Help

[Rowan Arquest]

kay, I am currently DMing (again) a Gesalt campaign. In
case you are wondering, a Gesalt (Unearthed Arcana) campaign means
that the PC's and BBEG's have two classes that level up in tandem,
where that character gains all class skills from both chosen classes
and the better saves, BAB, skill points, and HD.

Currently the party is 6th level (sort of), with a level 6 Half-Elf
Scion(Nomad)/Urban Ranger, a level 6 Human Psychic Warrior/Rogue, and
(here is the sort of) a level 4 Werebear Fighter/Barbarian (I have
ignored alignment restrictions for both Werebear and Barbarian). I was
planning on adding a Cleric/Fighter but now two of my friends want to
join in, AND THEY ARE ALREADY DOWNING LEVEL 12 ENCOUNTERS!!!!!! HELP
ME!!!!!

How do I keep up the intensity and challenge without out them leveling after each encounter. And this will most likely have 2-3 party members added to it depending on if I can get one of them to play as the character I made.

[evil-frosty]

Ok this post is a little different then your last one. Make it less combat oriented more problem solving. Enemies never stay for a straight up fight. Spellcasters cripple certain party members. Give every possible advantage to the monster.