Yep. I always like to go a bit (.3ish) bigger on sealed boxes for the added extension but if you go too far like in this case what happens is that the driver loses suspension control due to weak back pressure and in turn you lose upper bass output and power handling. What you gain is low end output. 3.07 cu. is approaching free air with that sub. It's even a little big for a ported box, but your only options are to somehow convert it into a ported box or scrap heap it.
Or I guess you could leave it as is or throw some huge rocks in there. Just watch how much power you send it as it is now. It is a setup where smoked coils are pretty common.
i think thats too much cuft - u can take a look at different brands to get an idea of what a sealed box cuft shud be like ...for a sealed 12" its usually about .75-1.5cuft .......