...Does following the canalway slow you down much? I typically ride at about 14 mph without gear on my bike. Fully loaded with camping gear and with rest stops, I probably average 10 or 11 mph, but this is on paved highway surfaces. Did this surface of the canalway slow you down much?
My opinion is that unpaved, improved trails such as the EC will slow you down about one gear. (I have heard that trikes are affected more than bikes, which makes sense as they have 50% more wheels.) In any case, you trade off a little speed for a nice traffic-free trail. Your call.
Rolled stone chips/dust make a decent riding surface. Unlike dirt or gravel, it retains most of its traction when wet, though wet conditions will result in a pasty coating on your bike. You do kick up a bit of white stone dust, so if you're towing a kid trailer you want to make sure you have a full length rear fender or a generous mud flap. For the front wheel on a recumbent tandem too, so your stoker isn't breathing all the dust.