The higher the ratio the peakier it will be.
If you are looking for daily flat response, lower the ratio.
Im doing a 1.1:1 with a platform 3 18. 3 sealed, 3.25 ported @ 45hz.
2 cubes sealed per sub is really small, do 3 cubes, maybe seperate the sealed chambers with a baffle. Mount the subs with the motors in the ported section, will aid in cooling and if ur burning coils u'll be able to smell it.
3" coils have a limit to the abuse, no matter how small the chamber is.
Design the box right with as little rise as possible and you what need tones of power to be loud.
So i say do 2.5-3 sealed per chamber, seperate chambers. and between 10-12 ported if you are sticking on the 2:1 ratio.