If you just build it right you will be way happier
And 2x rise is a good goal to hope for so don't expect much less if any than 2ohm
Also why not just build it proper and let her rip
Your box may unload quickly below tuning so be sure to set your ssf to not damage the sub, but iirc these are free aired on 2500 clamped.... So I don't see much of an issue
Why not just build to optimal specs and power accordingly
If you are trying to build a do all box I don't think making a big box is going to get you to your goal.
If you just build a good box and tweek it a little to optimize it you will be happier IMO