Tuning a box for my new RE Audio SRX10D4

[eyeballeater]

So I just want to make sure I'm getting this right before I start.

My current enclosure is .77 cu/ft and sealed.

The manual for the SRX10 calls for tuning at 35Hz
According to internet port size calculators, my port needs to be 2" wide and 7.51" long to achieve the recommended 35Hz.

Is this correct?

Also, how much (fiberfill, pillow stuffing, batting) would I need to bring my internal volume up to about 1 cu/ft. Would I even gain anything by using it or should I just leave it? Manual says ported enclosure should be .65 - 1.0 cu/ft plus PD. What is PD? Port displacement?

Thanks for helping and teaching me about this kinda stuff

TIA