[MpG]

Swiftech's fan spacing is only 15mm, which basically puts the fans flush against each other. Other rads such as the Thermochills/Fesers use wider spacing, and incorporate a build-in shroud, the combination of which serves to open up a significant air gap between each fan that air can travel through (without travelling through the fins), so that's where the gaskets are much more important. So if you want to run that rad without a gasket, you can probably get away with it.

If you're feeling fancy, or you're running higher powered fans that might cause vibration, you can grab yourself a roll of foam tape from your local auto/hardware store and line the edges of each fan with the foam before screwing it down. Just make sure the foam doesn't bulge into the blades, or you'll hear it really quickly.