*I think* I might be finally getting somewhere after much experimenting.
1) Plot a route in google
2) EasyGPS FULL to get .gpx file
3) Open in Bikehike and go through and add coursepoints. I use the generic and custom name them i.e. 01 RT, 02 SO, 03 2E etc
4) Download from bikehike to a file.
5) Do a quick find and replace wpt to rtept and add a <rte> and </rte> around the route.
6) Open in Map Source and filter down to 500 trackpoints.
7) Transfer to the etrex, show the track on the map and navigate the route offroad.
I have yet to try this though
I attempted it the other day but the .gpx file wouldn't open in MapSource. I realise now that this was because I omitted to enclose the route in the <rte> bits
. So instead I used it as downloaded from bikhike but that of course uses waypoints instead of routepoints, and we don't have as many of those to play with.
I'll be testing it on the Dun Run.
Thanks for all the advice