Heat Sink inside the Auber box?

Hey folks. As I finally have all of my parts and pieces for my e-brewery, I'd like some input regarding the heat sink. I have the vented Auber project box, and I'm wondering if it would be OK to mount the heat sink (40amp SSR) inside the box, up against the vents in the back. I'd rather not include a fan, since real estate is tight in there, but if people think I really should, I could.

Here's a photo. What's the verdict?

I have mine on the outside, it never seems to get very hot. You might be able to get away with it.

I have mine set up with the heat sink inside the Auber box towards the back and it seems to work well. This is for my rims and its only running at 120v...