Advancing monsters smaller

[ffone]

In certain situations I would like to advance a monster for an encounter (to increase its CR), but don't want to advance its size as well. I might even want a smaller size. For example, a villain's house with golems who can easily fit through doorways. (The SRD golems are all Large or Huge.)

Is there a template that'll increase a monster's CR but decrease its size? Or a decent rule of thumb for such CR adjustments? For example, a creature could be shrunk via a permanencied Reduce Person...if it's a monster that primarily benefits from a larger size, what's a good CR adjustment? -1? (SRD advancement suggests +1 for a size increase, although that comes along with bonuses to Sr, Con, and natural armor that far exceed the adjustments for Enlarge/Reduce person).

[The Mentalist]

With the loss of reach and the negatives to Str and AC (Con too if not a construct) I'd say that it's -2 to CR even. A medium sized Ogre would be a solid CR 3 I think. This obviously doesn't work for something like a Balor, who'd get a -1 I think (reach is AWESOME!)

A good general rule would be:
Melee brute -2
All purpose (ranged and melee) -1
Ranged -0 (or even +1 in some situations)

[Coidzor]

Dungeonbred template might be of interest to you. Dungeonscape, IIRC.

Don't believe it influences CR, but, well, you can increase the HD and thus increase the CR but apply the template and result in a more powerful but sleeker version.

[ffone]

With the loss of reach and the negatives to Str and AC (Con too if not a construct) I'd say that it's -2 to CR even. A medium sized Ogre would be a solid CR 3 I think. This obviously doesn't work for something like a Balor, who'd get a -1 I think (reach is AWESOME!)

A good general rule would be:
Melee brute -2
All purpose (ranged and melee) -1
Ranged -0 (or even +1 in some situations)

I agree that it's a big 'loss' for a typical melee brute....but since SRD size increases from racial HD are +1 CR, and confer more bonuses (usually +8 Str, -2 Dor 0 ex, +4 Con, +2-5 natural armor, and the usual size modifiers) than Enlarge/Reduce person (+2 Str -2 Dex or vice versa), I don't want to create a situation where I could advance a monster enough to enlarge it once, then Reduce it in my custom way, with a negative minus to its CR and a plus to its abilities. (Or, including the 2-4 racial HD that changes the size category and also confer +1 Cr, I'd get +2-2 = +0 CR with an increase in the monster's HD and stats.)

Or perhaps you're saying I should also houserule the size increase is +2 CR.

[The Mentalist]

Or perhaps you're saying I should also houserule the size increase is +2 CR.

To say that the CR system needs houserules is to say that a fish needs water. It doesn't work without them, there are numerous examples of CR imbalance.

What I recommend is you take that chart from earlier and reverse it for size increases.

[Greenish]

In certain situations I would like to advance a monster for an encounter (to increase its CR), but don't want to advance its size as well. I might even want a smaller size. For example, a villain's house with golems who can easily fit through doorways. (The SRD golems are all Large or Huge.)

Is there a template that'll increase a monster's CR but decrease its size? Or a decent rule of thumb for such CR adjustments? For example, a creature could be shrunk via a permanencied Reduce Person...if it's a monster that primarily benefits from a larger size, what's a good CR adjustment? -1? (SRD advancement suggests +1 for a size increase, although that comes along with bonuses to Sr, Con, and natural armor that far exceed the adjustments for Enlarge/Reduce person).Give 'em class levels. Burn a feat on Tunnel Fighting (RoS) to remove AC and attack penalties when squeezing, and a Large creature can fight in spaces meant for medium creatures just as well as said medium creatures. (Well, it halves the speed, but even then a normal Large creature is as fast as a medium one in armour.)