You have an Iron Cobra and the beaters are too heavy??  Really???  Those are some of the lighter beaters I've seen!!  Iron Cobra's come with the small flat round beater right?  They should have an adjustable weight on the beater shaft, you can move that further down the shaft, or take it off.  

If you want a really light beater, Slug has a titanium shaft beater, i'm sure it is rather light.  

hmm weird, i agree rlhubley on the IC, they are already some of the lightest beaters i know

wish i could help, love the cobras.  use 'em on all my pedals (even the speed king ... SACRILEGE!)

so i guess this post was useless.

sorry