Kicker subs are known for specific box size requirements, especially the solo-barics.
You can do harm to a speaker if it's not in the proper size & constructed box.
If it recommends 1.0 cu ft max., I'd account for the internal bracing, sub magnet assembly and figure that into the 1.0 cu ft, but not much more.
If your max size is 1.0 cu ft & you use 1.30 cu ft, that's about 20% over & it could shorten the life of your sub or give unwanted performance (same with a box that's too small or poorly constructed).
The actual internal volume can be cheated a bit with the amount of poly-fill you stuff in the box, but I forget the specifics.
The 15" Original (Round) SoloBaric I have states 1.5 cu ft maximum AND gives specific dimensions for the box size to maximize performance.
The spec sheet I received with my sub clearly stated: NO ported box, NO freeair install, NO oversized box, NO udersized box, ONLY the recommended box size... and give it as much power as possible-up to the max. 750w RMS. I'm working on the last one.
I've had my SoloBaric for 15 years or longer, without any problems - but it's been in the same enclosure it came with (built to Kicker specs).