Guidelines for swift spell creation?

[drdevoid]

I'm pretty new to the swift/immediate action thing. The only guideline I can sense for creating a swift spell is that, generally, a spell that has an effect measured in rounds simply has it's duration shortened sharply to create a swift spell version.

Does anyone have an idea how to do this for direct damage spells? The only spell that I have for reference is a Sean K. Reynolds spell from the WotC site:

Kaupaer's Quickblast
Transmutation [see text]
Level: Sorcerer/Wizard 1
Components: V, S, M
Casting Time: 1 free action
Range: Close (25 ft. + 5 ft./2 levels)
Target: One creature
Duration: Instantaneous
Saving Throw: Reflex half
Spell Resistance: Yes

A tiny sphere of cold, electricity, or fire speeds from you to the target and deals 1 point of appropriate energy damage per caster level (maximum 5 points). The spell has the descriptor for the kind of energy you select; for example, this is a [cold] spell if you choose a sphere of cold.

You can cast this spell with an instant utterance. Casting the spell is a free action, like a quickened spell, and it counts toward the normal limit of one quickened spell per round.

Material Component: A drop of quicksilver and a blue, yellow, or red glass marble.

From this I guess that 5 points per spell level or say 2d4 per level is a dice cap (perhaps 2d6 if it requires an attack roll?)