Good thing I don't have the codes for the nuclear football!
There must be 3somebody in VT.
I don't know if it's the same in dogs, but for people, steroids put on weight big time. I don't know if the med itself helps to cause it (like some meds do all on their own) or the fact that you could pull up a chair to a buffet with a napkin tucked in your shirt and go to town, when you're on them!
If there is a place that does things like laser therapy, underwater treadmill (for weight loss - and not a lot of water needed for a Corgi!) you could try that.
And 8# weight loss will take some time to do. That's like 20% of his body weight right? I think (not good at math) that would be like a 200# person losing 40#. I am not sure the best way to do that with an older dog.
But I am sure you can do it!