Help with 2 10" Sundown Uv2 slot port design

[Crankit89]

Hey guy's this is the second time building a box. I have the dimensions 41"×15×12. That's over all. I think I wanna go with Birch or something other than mdmf. Due to the weight.  I'm lost on the slotted port design part. If I could get some help with that I'd appreciate it.

  I'm going to Double baffle the front. It will be going in an 06 lincoln town car on the top shelf of the trunk. I'm kinda lost and trying to understand the tuning part. As far a port length and width. 

  I have built a box Previously with 2 12"  American Bass  XFL's and it slammed. Oh and I'm thinking about running a salt 4k on the Sundowns thanks for the help looking forward to the whole build!