First problem: Trunk is not sealed. It will take a lot of effort to do so. There are gaps all over the place, the rear deck is perforated like crazy, and simply, it's tough to do. Infinite baffle only works if the trunk is COMPLETELY sealed.
Second problem: Finding a driver that can handle IB. Most drivers cannot, because it requires very strong suspension, and you need to pay a lot of attention to the driver, because it's SO easy to over-drive your sub and destroy the suspension. An L7 will explode (literally, pieces of the cone everywhere), it wouldn't be able to handle it, as would most subs.