Well here's the deal. I've ended up with City Select, thanks for the input. The maps for my Oregon to Virginia route take up about 100 megs of the 76C's memory (the Roads & Rec data for the same route are about 25 megs). There's obviously a whole lot more data there with City Select, also obvious when I compare the respective renderings of the local scene.
As for the waypoint issue, there are something over 1800 points in the ACA files that cover my whole route. The 76C only holds 1000 points. I'm sure I could toss out a bunch of points by selectively deleting route points marking curves in roads and the like. But life's too short.
What I've done is to build a file that has the full data set in more densely populated areas, where the route might be more of a challenge to navigate. That's mostly in the midwest and east. I've tossed out large chunks of navigational points in the west, and in Virginia where I've pretty much already been over the whole route at one time or another anyway. Since I'm going to be mostly camping, I've kept all of the campground points for the whole route. I'll also be carrying paper maps.
As for the 76C on the bike, I've built an aluminum carrying bracket that centers the thing in my aerobars, which is very nice in terms of viewing distance for my eyes. I've purchased a set of 2500 mAh Energizer batteries; these seem to have staying power. I did an 8 hour ride yesterday, and running the thing with the data screen up most of the time (which is black & white, gives speed, averages, time, elevation, and a whole bunch of other possible numbers), rather than having the color map screen on full time & watching myself crawl down a long highway without any intersections, the battery charge indicator never went below full. I've also purchased a Maha MH-C204W charger, with is very light weight as those things go.
So far, so good.
I'll post an image of my mounting arrangement on my trip website in the next day or so. Those out there who would prefer to ride without GPS & other techno-gadgetry, have at it! Nobody's forcing this down your throat.www.nickevans.crazyguyonabike.com