You'd hate my Dart then... 10 lb nitrous bottle, aluminum fuel cell straddling the spare tire well (fuel pump mounted in there), two large solenoids (one for starter, one for car power), and the battery :p
(I did install a sheet steel firewall, the battery is enclosed, and everything is vented outside the trunk). :)
BTW I have three older BMWs. The '93's battery is under the back seat; the '97 and '98 have them in the trunk. They came that way from the factory by the millions (literally, 1.3 million E34 chassis alone). Doesn't seem to be a problem for the Germans!
