can someone double check my modeling QES820

[Ummagawd]

HI all - I don't have a windows machine and thus can't use WINISD, so I've been playing with speakerboxlite.com

Can someone cross-reference this to see if what I'm seeing is true?
- CDT QES820 8" sub
- about -3db @ 28hz
- flat 0db @ 35hz and up
- in a vented enclosure with the following parameters:
Vb(cu.ft) = 0.678
Fb(Hz) = 31.6
F3(Hz) = 28

Fingers crossed if so!