Thanks for this suggestion Richard. There has been some discussion about this before and as a result we've added something to our Feature Requests list (number 12), where people can vote for the changes they woulkd most like to see.
Option for the GPS map line could be adjusted so that it plotted an optional number of metres from the centre of the road eg. in UK we ride on left, so plot 2m to left of centre line.
This would have two benefits:
1 - Less gps error and false 'off course' messgaes
2 - When plotting out and back, the out and back routes would not run over eachother so adding direction / wayoint info to the desired direction would be simpler.