Oops, didn't see that!
I couldn't comment on the combination of adding at the end of the boil then dry beaning, as I've only ever dry beaned. But with a double addition, I would be careful that you don't overdo the roasty/coffee flavour though!
If you were going to smash through it in a couple of days, this would be an amazing chance to see how the flavour changes with time.
I'd be hesitant if you weren't going to get through the beer quickly though - when I dry beaned a coffee-vanilla porter, it was perfect after the beans had been in for 2 days, but I couldn't bottle until day 3. By then the coffee was overpowering and had suddenly also imparted a sharp flavour that I could only describe as green wood (like I imagine a small twig from a sapling would taste if you bit into it!)
