make sure all fields are clear, then
enter qes then hit tab, enter qms
hit tab a couple times and let it calculate qts
hit tab a few times to move to mms
enter mms, re, bl, le, sd, xmax, and pe
by using tab after entering each data, it will calculate what it needs to
i no longer get any conflicts
sometimes the specs calculated don't match exactly the manufacturer specs, but its only rounding type errors, so it is not material
Take a look at cone excursion, you should keep it around xmax which is 14mm for that driver. Another thing to watch out for is air velocity, Winisd recommends 17 m/s but with flares I think you can go higher.
I suggest keeping the external dimensions simple like 26x26x26", not 25 13/16 x 25 1/4 x 26 15/16 or something weird like that.
no need to tune very low, the plate amp likely has some sort of high pass filter around 20hz or so.
another option is two 4" diamter tubes, 23" long for an 18hz tune.