I have found that the spot welds are a little easier to find on the inside.� Access was reasonable from the inside, but I used a Dewalt drill bit.� The cutter may have different challenges I'm not aware of.� I cut from the inside so the exterior side of the panel would need less work to look clean and flat.� Honestly, I think you'll have success from either side.
If you need to clean up the welds on the inside, using the edge of a cutting wheel in your grinder works pretty well.� Just gently trim away the excess with light back and forth motions.
Once in the tight radius, I switched to a die grinder with a small cutting wheel.� Hind sight...Back there, welding and grinding will be easier from the outside.� It gets pretty tight back there.
Tim