Would you have a photo of the top and bottom of one of your boards? I've read quite a bit about the single-point grounds, yet the Sparkfun protoshield has such nice, tempting, 5V and G, buses (if you will) down the sides that would be so easy and clean to connect to. Would that be a mistake? Instead, should I do something like you're talking about to get the connection points as close as possible to each other? At some point you probably have to start worring about hitting devices below on the Arduino board itself.