Well, there's nowhere else on that bike to put a battery that large other than that rack. even a smaller battery, if I had to mount it on the downtube, my wife wouldn't be able to step through, her hips and knees won't let her swing her leg over the seat.

yes, the bike is very tail heavy, but it doesn't have much of a tenancy to wheelie unless you really throw yourself back. hence my thinking mid-drive and water-bottle battery for my lighter weight hybrid build.