Yeah, I like that rad mounting too. Technically, you're getting slightly cooler air this way, rather than grabbing what's leaving the case, and it'll be a cinch to vacuum dust out if it becomes a problem. And if you ever feel like a little more cooling power, just bolt a couple of fans on the front of the rad for a push-pull setup.
Watch the opening that your tubes are going through - some of those edges look a little sharp - wouldn't want them to rub through your tubing over time. You might have problems with the pump trying to make the case vibrate. If so, some sort of soft-mounting might be necessary, but hopefully not.