It was tuff finding a good sub at .087 to be honest. I can easily buy another if I find one that would compliment the box better. The 1.15 was the lowest so I'm hoping the polyfil will help in that aspect.putting a speaker in a smaller than designed box will make the response roll off slightly faster below Fs. in other words, bottom end will be slightly cut off and it can sometimes make for a boomy sound. the upside to this is that you slightly increase potential power handling capabilities.
adding polyfill can sometimes make a box produce a slightly deeper tone, but its subtle. rue of thumb is 1lb for every cubic foot.
if you already own the sub and the box, add just under a pound of poly and just go with it. EQ the bottom end and pay attention to the 50Hz+area, you may need to cut frequency response above that to stop the boomy sound. itll probably be ok though in all honesty.
It was tuff finding a good sub at .087 to be honest. I can easily buy another if I find one that would compliment the box better. The 1.15 was the lowest so I'm hoping the polyfil will help in that aspect.