Not sure why the 2 entries above appeared. I respect your views re the testing, always best to err on the side of caution. My method is to fill the rad with water with the orange handle valve closed. Then gradually open it once the compressor is ready. Increasing the pressure in 1 bar increments until I have the desired test pressure then close the orange valve. My opinion is then that there is actually very little actual air in the rad. As the cast iron rad are rated at 6bar but have supposedly been tested at 10 bar I only keep the 5 bar on for about 30 minutes. I will then drop it to 2 bar and leave overnight. Testing with water does help in indicating where, if any ,the leaks are.
Regarding the feet they are white to match the radiator. This is not the same rads as I have been testing.