You lookin for SPL? ... find the cabin frequency and tune around that, use an aero and burp it, won't be musical probably tho... but might give ya' a headache... lol. You'll lose SPL tuning low but it might "sound" louder to you. I'd probably do a 35-36hz tune if ported just to still have some lows. It wont slam decaf at that tune but will be a decent compromise. H*ll most enclosures are a collection of compromises. Probably need to tune in the 60's for max SPL in a small truck.