2 subs 1 box

Hello all, I now already have 2 2ohm power acoustik mofo 15s and 2 audiopipe 1500.1 d amps. Currently, I have 1 sub and 1 amp wired to 1ohm in a box I made with some help from posts on this forum (thank you all!) and WinISD that works well for me. However, I'd like to add the second woofer and...