I can't speak for the DRAK, but the Big Sucker has a bare filter and I do not run anything over it. I have been caught in some pretty heavy downpours and have never had a problem. During an Iron Butt last year the bike and I endured about 3 hours of heavy rain with it and she made it all the way with no issues.
Not saying you should, just relating my experience. I have been looking to pick up a different cover for long trips just in case I hit rain, so I have thought about the issue.
I don't ride to putt, I putt to ride!
8541hog.net 05 Wide Glide