No, "spkg -i" wouldn't work at all. "spkg -u" would upgrade the package.
Actually, I think this is written in the guide, but maybe I haven't stressed it enough. You don't have to use "-i" and "-u" switches with spkg. Running just:
will either install a package if it's not already installed, or upgrade it if another version is already installed. spkg knows what to do in either case.