My TM is 32 liters and my normal DD is 31. I'm 6'0 and my TM is stock 5'8. Feels perfect for me and I love it.
I'd be more concerned with length than volume. I'd suggest sizing it length-wise like a Dumpster Diver / Stubby.
I am probably going to order another one, 5'8 but add some thickness and/or width. I am also intrigued by the round tail.
I have been slowly narrowing in on boards/dimensions that work for me. Slowly is the incorrect word as I have YOLOed several boards over the year with a bit of one step forward and two steps backward. I am nearing 50, and going for it now before it is too late ! By no means, do I feel 50. As I realize more and more, most of my boards were/are either too long or too wide. Once I started getting more right-sized my surfing progressed significantly.
As much I will likely be better off with bigger board, nothing is more enjoyable than the feel of the shortboard.
Last week, I got 5' 4" Varial Plasmic and holy crap has this board been super fun. The sizing inherently works with my feet position. I thought my feet position worked on other boards, I stand corrected. It is like a switch went off, I am able to push into the board and make solid turns and generate speed. My motions are the same, but the smaller board unlocked the potential. I am beyond stoked at the moment !