I’m certainly not that detailed. I put it on the diagonal and never have issues. The amp is so quiet for a SE. Personally, I do it on the diagonal since the tabs make it the easiest to do. I start with one of the predrilled holes near the center of the chassis and angle it away.
If there is a lot of noise, it is probably not the placement of the OT. I’d troubleshoot everything else first. Then, if you think you can get it quieter by adjusting the OT to a perpendicular orientation, let that be the last resort.
Thats my 2c.