I've never experiemented, but Guitar Player recently reviewed the big MArshall Plexi reissue. They noted in pass that the heavy woven salt-and-pepper grill cloth takes some of the highs out. In this case, they though it was a good thing, since they were of the opinion that the 100-watt Plexi is loud. Imagine.
Experimenting wouldn't be all that hard - just tape samples over your cab. Buying the samples would be more difficult. Grill cloth ain't cheap, and you always need to buy at least a yard.