Does anyone think that pre-cooling the ephedrine and rp mixture before mixing the iodine would be a good idea? perhaps this could be a way of preventing a more violent rxn.

No. Just set the beaker/flask/whatever in an ice-bath as directed. There's no avoiding the thermal properties of the reaction at hand. Nor does it hinder the end product rather it is 100% necessary.

but wouldn't the rxn be somewhat slower on account that the particles in the reactants are moving so much slower?

actually it works quite well to put your precurser in the freezer before you mix them, and then after you mix them to put the flask in an ice bath for the first part of the reaction. It slows it down quite a bit and makes it not quite so crazy.