Hi, I've read the other post on this subject matter. I have one question, so can a start capacitor be used as a run capacitor and vice versa. As long as it sized correctly there is no physical difference between the two, am I correct?

 

The run type are continuous rated and are usually oil filled/paper, they can also be used for start cap but the value is generally too small for start.
The start cap is only rated for short periods because of the danger of overheating, due to the larger size generally required they are electrolytic back to back to allow AC service, and cannot be used for run mode.
They are usually marked or sold as AC motor run or AC motor start.
Max.