That gives you ~2.25ft^3 with a ~39hz tuning.I thought my original box would be to big but maybe not. How about...
W20xH16xD20
2.87ft^3
2.25 PW
14.5 PH
20 PL
I got closer to 2.4cu/ft tuned to 37-39hz. Keep the same airspace and just lengthen the port to lower the tuning. You will have to keep playing with the dimensions. Type r's like 30-33hz the best. 35hz will work but you are sacrificing low end too much imo.I thought my original box would be to big but maybe not. How about...
W20xH16xD20
2.87ft^3
2.25 PW
14.5 PH
20 PL