2 deafbonce apocalypse 4514rd2 in sentra

Removed all seats except driver in 2008 sentra. Cut out rear deck all the way to windshield added alternate bracing. I have 3 agm 1 lithium battery 320 amp alternator and salt 4 for 2 deafbonce apocalypse db4515r d2 parralel at .5 ohm

I have built 2 ported boxes and was loud af but decided to try 6th order and failed. Any advice on exact box parameter for both subs would be much appreciated. Also they are 135lbs each so subs up is the easiest way to mount in such a small area. The terminals started arching from the aluminum basket so im struggling to find an alternative terminal option