I give it a route with points ~100m apart...
Is there a setting in mapsource for this?
I dont think GB uses Mapsource. He has an Edge 705 which effectively does not have max route/trackpoint limits. Mapsource comes from the era of pre-Edge products such as the eTrex which do have limits, most noticeably, 50 points for 'follow road' routes and 500 points for tracks.
In Mapsource you can filter tracks to specify a minimum inter-track point distance for example. See Track/Properties.
As it happens, I recently processed the K&SW 600 track to make it eTrex friendly (Ian provides a single 6000 point track). My objective was a set of routes with 50 waypoints for follow road navigation, and static tracks with 500 points.
Steps were:
1) Use WINGDB3 to Split & Filter the track and convert it into Routes with Waypoints (Opt21, Split after 150km, Filter to 50 points per Route), save output GDB
2) Use WINGDB3 to Split & Filter the track into manageable lumps (Opt24, Split after 150km, then Filter to 500 points per track), write/copy tracks into Stage1 output GDB
3) In Mapsource, select waypoints, change from default markers to nice Blue Flags (I use Red flags for main controls, Green for Infos).
However track/route points are not evenly distributed though the track/route. It looks like WINGDB3 selects which track points to process based on change of direction. The consequence is that there can be large gaps between track/waypoints and track/waypoints tend to cluster around towns. Still, it looks 'good enough'.
As usual, YPYPATYC. HTH