Most airfields have some prescribed way of leaving the circuit. End of upwind, end of crosswind, whatever. Why not use that as the start of your track?
In any case, the size of the circuit is relatively small compared to the length of the track, and in VFR conditions you should be able to see at least the whole length of the circuit. So if you plan your track to start overhead the airfield but actually start your track at the end of upwind, you are now maybe one mile off track - something that should easily be correctable visually in the next few miles.