After being on now for a few days here are the temps I have measured with a thermocouple:
Front Panel 3.5mm jack: 88 degrees F. Inside about 1/2 inch its 90 deg F
Front Panel RCA Jack: 86 deg F
Front Panel Screw Upper Right Corner: 85 deg F
Top middle case: 87 deg F
Side center/middle case: 85 deg F
Rear Panel Middle Regualtor screw : 89-90 deg F
Front panel 1/4" jack internal about 1" insertion to back of jack : 93 deg F
The entire rear panel is relatively uniform in temp distribution.
Then entire case is relatively uniform in temp distribution as well.
I have no ventilation holes in my build.
I think I will add the holes / slots in the back panel to see how well that goes.
My gut thinks not that much.
I also had a 1/4 headphone plugged into the 1/4 jack all the time except when I measured the internal temp there. So this precluded any air entering that opening.
All in all the case is slightly warm at a 88-89 temp etc.
All the best