baffles inside exhaust pipe?

Has anyone used baffles like this that are intended to go inside the exhaust pipe? I want to use a pair of shorty mufflers on my KZ400 because they'll fit nicely with how I'm building my bike, but I would like it to be a little quieter than the shortys will get it. I was thinking of running these in addition to the mufflers, but I'm wondering if it would be too much restriction.

http://www.lowbrowcustoms.com/baffles-for-1-1-2-exhaust-pipes-universal.html

if experience is anything to go by, they won't make the slightest difference to either restriction or noise