Assuming you have 8' ceilings I'd say you have the right panel as
you're at about 0.75 watts per cubic foot.
I have just over a watt per cubic foot in my room and it's way too much. My snake room is in the back of my garage and even today when it's zero degrees outside my heaters don't run anywhere near full. I can even leave the door cracked while I'm working in there and can hear the thermostat cycle on and off.
Hey, if you don't mind and assuming you have a temperature gun could you check the surfact temperature of your panel for me? Check it in several spots and post the high/low numbers.
Here is a picture of my snake room. The cove heater is the tan strip up near the ceiling:

The problem I'm having is that they need a certain amount of clearance meaning I can't build or stack cages up as high as I'd like. This is why I'm considering replacing one of them with a panel. I can mount it on the ceiling and have it radiate down onto the work area and not at a cage stack. This will give me a lot of options for using the wall space, at least at that end. Below the other heater will be reserved for hatchling racks and a work area.
Mine running on 220 volts they are remarkably efficient. Way under 3 cents per hours. I could heat that room to 100* when it's below freezing in the garage for less than that.
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Currently keeping:
6.10 Gonyosoma oxycephalum (Javan, mixed colors)
0.0.4 Rhynchophis boulengeri
1.1 Philodryas baroni
1.1 Lampropeltis triangulum multistriata
0.0.1 Rhamphiophis rubropunctatus
0.0.2 Morelia viridis (Aru & Merauke locale types)
1.0 Rhodesian Ridgeback