Help with tiny box and X8’s

[Rapture2-1]

Hey guys I have a Ford ranger single cab daily driver. Not a lot of space in the rear being so little. Most people do tiny shallow mounts but not me. 
 

currently I have a single X8 v3 d2 in 1 cu ft net and a 12sq in area slot port at 32hz. Now honestly it kind of murders the lows. I’m blown away by it. But it lacks heavily in higher frequencies. 
outside of that I want more. So the debate is how many 8’s I can fit? It’s looking like two, I’d like to do three but making a large enough port complicates things a bit due to depth. 
 

I can do 11.5” tall, 11.5 deep and around up to 50-52” of width. I’m a novice to box design so I need some help. Two goals are louder and actual bass outside of the 30’s hz range. Seems like it goes from quiet to very loud. Box may be too big but I went off sundowns recommendations. 
 

Going to a 2 woofer setup or 3 I’ll be adding in a Salt-2. I just need to run another line of 1/0 for it. Already did my alternator and battery. Might also toss in a second AGM if needed but we will see. I understand 2 will be a .5 ohm setup so I’ll have to be very mindful of the power going to the two woofer. Though I wonder if the salt 2 @1.33 ohm load would properly power 3 x8’s 

 

‘’currently running an sae 1500. Will likely end up using it for two shallow mounts in my race truck

 

I’m pretty good with electrical but not so much audio or pneumatics so I’m open to any and all critiques and advice. 
 

Edit: I usually try to do slot ports but again always open to advice 

[Joe X]

For a test block the port in your enclosure to run it sealed, if run like that you can listen to higher bass normally it means that the box needs to be redesigned to different specs.

[Rapture2-1]

Okay I’ll try that out this evening. On the new box I was thinking of going down to .6-.7 cubes