I’ve been researching since I posted the thread. And I’m seeing that more people put it horizontal. And most people say it doesn’t matter. But that there are more reported cases of RROD, and other problems when laying horizontal. But that could just be because there are more people putting it horizontal…
In the end, there are reported issues with both ways, so it all just depends on which way you think looks better, and how it fits into your setup.
Right now mine is laying horizontal and seems to be working fine. Hope I won’t have any issues (crosses fingers).