A few (including myself) have tried... doesn't work. I figured I'd just have to change the focal length a bit more than the Seouls, but no go. The Crees won't focus at all, at any distance from the optic. The Crees have a different beam angle. The Seouls work because their beam angle is really close to the Luxeons that are installed in the Coast lights. BUT, the new Coast models coming out are using Crees, so those will be upgradable with new bins that happen to come out.