Is that L x W x H?
If so, the
JBL Room Mode Calculator shows the imbedded image. There are weak clusters at ~50Hz, ~100Hz and ~158Hz, but not so bad.
But, since you are doing all this advance planning you really should check out the
Room Reverb / Sabine Calculator and Charts site and work through your possible RT60 using Sabine values of various wall/ceiling/floor materials. You could end-up with a really sweet place.
As well,
Linkwitz has some great stuff, and a
Room Mode calculator, too. However, my quick model of
your ratios shows you are
WELL ahead of the game! Nice! ;)
.
.