I tried to play a little bit with the slow effect of frost spells, so that I could try new values to make targets even slower.

Seems this effect modifies the "SpeedMult" attribute of the target, but I tried for example changing the slow from 50 to 90 on Frostbite and nothing happened. I don't even think the original slow works consitently in fact. Also, the way this effect is implemented seems a little odd, using both 'detrimental' and 'recover' modifiers. In the end, I concluded I simply don't understand how exactly this effect works and how to modify it.

Anyone with experience regarding this effect?

http://www.creationkit.com/Magic_Effect

according to the wiki:
Detrimental signifies an effect that applies a (-) modifier
Recover means that modifier won't stick around once the spell wears off

Did you try using a lesser value? e.g. 10
the spell might behave oddly since it is affecting SpeedMult (which is a multiplier instead of a raw number?)

Played around with it some myself and it appears to be buggy. I got no slow effect when I changed the magnitude from 50.
You can also test SpeedMult on actors using the console in game. I don't think they animate correctly at values below 50 (at 10 they do goofy run in place type running)

Yes, I tried many different values, including values between 0 and 1 (since SpeedMult seems to be a multiplier).
I think I'll have to research a little more about this "SpeedMult" value and how it affects the current speed.

Thanks.

you might also take a look at the AlchDamageSpeed Magic Effect
it uses a modifier called "MagicSlow"

The thing about the slow effect is that it is Peak Value Modifier so the effect is limiting your speedmult to 50. Wisps have an ability that lets them move hella fast when they run out of magicka, its something like 200 magnitude wispspeedboost (dunno the actual magic effect) but it's a Value Modifier meaning that if you set the mag to 50 you'd be running at 150% your normal speed. Also you can check the players speedmult in game with `player.getav speedmult` it should be about 100 normally

Sure. That's why I thought that just changing Frostbite's magnitude to, say, 99 should have dropped the target's speed to 1 (since it's a detrimental effect). Also tried to change Frostbite mag to 1, maybe hoping to set the maximum target speed to 1.. But seems things are not that simple unfortunately.

Not sure if this helps in anywaybut here goes.
I copied the Frostbite spell multiple times and changed the magnitude from 50 to 100 and duration to 25 on the slow effect
I tested this on the Whiterun guards.
Using the console command, the guards normal speedmult is 100.
The normal frostbite spell reduces this to 75.

The copied frostbite spell (100 mag) altered the speedmult to 50

Setting the magnitude to 150, reduced the targets speedmult to 25

Setting the magnitude to 200, reduced the targets speedmult to 0, however had no effect. This would seem to make sense as i would hazard a guess at the way a slowing effect is applied to the target is as follows:
(normalspeed)-(normalspeed*speedmultiplier) where the speed multiplier is defined between 0 and 1. So speedmult of 75 would be 0.75
The last test i did was to set the magnitude to 198. This set the targets speedmult to 1. This effectively rooted the character but did not prevent them from acting or using melee power attacks if you were close enough. However it did seem to cause bugs with such a high value used when the effect wore off.

The slow effect has no effect if the target already has a speedmult of 0

No what you want is to change it to a value modifier like the wisp ability http://i.imgur.com/ig0gP.png

Also the recover flag is used to return whatever values you effected back at the end of the spell (otherwise the effects could stick)
http://www.creationkit.com/Magic_Effect#Flags

I think this helps, yes. Thanks.
I'll try to play with these values a bit to see how far I can go without reaching the point where it casues bugs, as you said.
Last time I tried to apply huge slowdowns with Value Modifier instead of Peak Value Modifier the enemies started running insanely fast after the effect wear off.

Just want to let you know that Speedmult only works well against other non-player actors, because the game will only check what th eplayer's speedmult is set to in specific circumstances for some reason (i.e. when you use inventory, sneak or sprint). This means any mods that affect player speed globally are impossible without something like Script Dragon, which requires an experienced C++ coder to use. Though I suppose it could be "safe" to alter speedmult in a script as a one-time thing, such as making certain races faster to boot.

I've ran into tons of issues with Speedmult myself trying to get it to work. The value appaears to be a % boost, so a value of 50 will be 50% faster, or 50% slower if set to detrimental. You ALWAYS want to set it as recover, otherwise it will permanantly change the speedmult values for the actor. If all the settings are even slightly off, the speedmult eeffect won't work at all.

In Fallout it used to be possible to force a reevaluation of an actor's speed by dealing 1 point of damage to their legs, and ResetHealthAndLimbs() implies there's limbs somewhere in the CK. Haven't checked out the full AV list, though.

read somewhere on another post (maybe on nexus?) that you can do a quick encumbrance effect via script or magic effect to force the player to reevaluate speedmult

Thats a shame, Bethesda should fix that really soon!!!
In the meantime: can someone come up with a solution for that?

I tried to create magic effects to adjust "carryweight" and/or "inventoryweight" none of which seems to achieve the desired effect of the game recalculating the targets movementspeed.