Been doing some measurements in my trunk in preparation for my next install and my intention is to install a pair of 15's in IB. The width of the trunk between the shock towers is roughly 34". The subs will fit but barely, gonna have to mount them from the trunk side, which is no problem. But with having very little baffle material around the subs, how thick should the baffle be? Will 1.5" be enough or should I go a bit more?