Importance of accurate course setting in overhead

[beammeupscottie]

This is going to sound like a stupid question, but I'll ask it anyway:

When you go off on a cross country, and set course in the overhead, how accurately overhead the runway must you be prior to taking up your track, to avoid flying a parallel course to the one you want to follow.

For example, (in the extreme), if you took off, flew around, and missed the aerodrome, then set course 10 minutes later, you would be flying a parallel track to where you wanted to go. I know this is an extreme example, but hopefully, It'll give an idea of what I'm getting at.

Thanks . .bmus