I've spent some of my time over the holidays re-visiting custom mapping & such on my Garmin 705 Edge. My initial interest was to be able to add local mountain bike trails to road and/or topo maps to run on my 705. I still don't know how to overlay multiple maps on the Edge (or, really, if you can even DO that..), but ultimately, I found nice maps (free) online that combined roads & topo and then created an .img file from an ESRI shape file which I merged with the compiled map tiles, did some file name changes & ultimately compiled & loaded on a micro SD card...so now the local trails I've been interested in exploring (I think about 30 miles of loosely connected single track over a rather large area where you could waste a bunch of time on roads - on a mountain bike - getting lost if you didn't have a map) show up as major roads on my Garmin...and I have the minor benefit of seeing topo lines as well (which isn't terribly helpful to be honest since the line interval is not terribly tight). Anyway, my point is that one place I didn't find a lot of info was here & I was wondering if other cyclists have found some interesting ways to hack/exploit/modify their Edges and would want to share info.