Hey, everyone, thought I'd post a post-mortem, given that it's been a good while.
The beer wound up
very good, especially with some citric acid added to make it good and sharp. The process of extracting the cherries in vodka did dull the taste a bit.
Only issue is that the ABV is entirely out of whack. Original K-Rouge is 8% ABV, and this one wound up being north of 14%. I used 4 gals of base beer at 8% ABV + 1 gallon (!) of cherry liqueur at 40%-ish ABV = ((4 * 0.08) + (1 * 0.40))/5 = 14.4% ABV, which is way too high, but still damn tasty.
The liqueur is also good on its own (I had about a liter left over). It's very obviously natural cherry, nothing chemical or synthetic to it. It has a pretty heavy alcohol heat, though, which I'm glad was moderated by mixing with the beer.
If I make it again (and I may not; it's a lot of money to buy all those cherries and vodka, and has to be kegged instead of bottled to avoid bottle bombs, so it takes up a keg), I would experiment with a long steep of just the cherries in secondary, but I don't have any idea how it would work out. Someone mentioned kirschwasser in the thread; I honestly don't know how well it would work.
My wife, friends and I are about 2/3 of the way through the keg at this stage (it's not a guzzling beer at 14%, whew), so be ready for it to last and last if you try it.
Some other things i might try:
* Scaling the base beer down to 5 percent, and the liqueur to 20%. That would yield an 8% final beer at a 4:1 ratio, but I have no idea how that would affect the body, flavor, etc. of the result. The base would no longer be a Donker clone, that's for certain.
* Different cherries. The ones I used were Walmart bagged frozen. Some sharper variety, or fresher one, might have gotten me closer without needing the citric acid.
If anyone else tries the recipe, post about it!
-Rich