NukeDOC
Retired Mod
I had a Pono tenor with the adjustable truss rod. I actually was able to lower the action a tiny bit into an acceptable range using that adjustment. I don't think the reason for having the truss rod was for action adjustment though.
truss rods are not generally supposed to be use to adjust action. they are used as somewhat of a counterbalance from the one-sided stress the string can put on the neck. when there is too much tension, stress from the strings can cause the neck to bow, thus raising the action in the higher frets. so, in a way, action can be adjusted using a truss rod, but only if it is in the process of straightening the neck.
you can see if your neck is bowed simply by looking down the length of the neck from the bridge, or you can do what i do... pick a string, either end. fret the string at the first fret with one hand. on the other hand, fret the string where the neck meets the body. if the string is just barely touching all the frets all the way down, then the neck is pretty straight. if the string is raised up off the frets, you have a bow. a little bow is not bad IMO. but its pretty obvious if youve got too much. if the strings are all touching the frets before you fully fret the string at the body, then you may have a backward bow... this is not going to be common in most ukes since they dont come with truss rods, but if you do, or if you check your guitar and its doing this, then you may want to back off of the tension on the truss a bit.