Cherries to a Russian Imperial Stout?

Just brewed a Russian Imperial Stout from Brewer's Best. Considering adding a 3 pound can of Cherry Puree into the secondary fermenter to add a cherry character to the beer. Box says 8.5% ABV. Figure the cherry puree will ferment and knock that up a bit. Anyone done this before? Is it a good idea at all? Looking for some guidance. It was a fairly expensive kit and don't want to screw it up by going mad scientist on the batch. Thanks for the advice in advance.

Two things:
1. Make sure your Cherry Puree doesn't have any preservatives in it, as they will kill the yeast and your beer will not bottle-condition.
2. You might want to think about upping the amount of puree. I've recently used a half litter of pure cherry liqueur into 10L of porter (1:20 ratio) and had almost no cherry character. For a beer this big, I'm really not sure that 3lbs would be enough

Cherry extracts might also be a consideration.

It might be easier to just add a kriek beer when bottling, similar to what's done for Three Philosophers. That stuff is yummy.

No preservatives, the brand is specifically tailored for beer and wine making. I want just a hint of the flavor without being overbearing. You think I should up the amounts? For a 5 gallon batch how many pounds should I add?

What about flavor, do these two seem like they would compliment each other, or should I just leave it alone?

Cherry Stouts have always seemed like a good concept, but they are always terrible. I take that back, Stone did a collab beer, Cherry Chocolate Stout that was actually pretty decent. Bells Cherry Stout was terrible. My first ever drainpour, and I HATE wasting.

Perhaps I'll just leave it at the 3 lb can to knock the ABV up a little bit without really doing anything to the flavor.

That's not a bad idea. It will give you a little fruitiness but not much else.

I'm pretty sure that with a Russian Imperial Stout you're actually going to decrease the ABV with adding fruit. You're adding sugars, yes, but you're also adding volume with all the water.

For instance, I've seen cherry purees at 10-12 brix (or 1.040-1.048 sg). If you add that to a 1.080 RIS, you're essentially diluting the OG down, not increasing it.