Banners in a fluid layout

I'm having a tough time determining if what I'm looking to do breaks Adsense TOS for tampering with the code.
Right now I'm leaning towards no, it doesn't violate anything & is actually a good idea.

I have a fluid layout, some visitors may get to the page with the area Adsense would be, only being large enough for the thinnest of banners.
Other visitors will have a space large enough for a 728.

Would using Javascript to alter the banner variables before the constructor is called be a no no ?

The way I see it, this would just be automating what I have to do anyway, which is determine which banner size fits best in the space & using different banner variables to accomidate.

What about after a browser resize, would it be a bad idea to alter the variables & refresh the banner area using a different sized banner when a visitor resizes their browser window ?

I think it says in the TOS that you cannot alter the adsense code in any way. I really wouldn't risk going into a grey area, just because you could get banned for good.

Definately not the response I was looking for, I'm going to follow your advice for the time being though.