I tune my H23.5 fractional rig with a Loos gauge that I bought at West Marine.
It gives consistent,accurate readings if you follow the directions.
The objective is to have a mast that is straight side to side, with the forestay and shrouds tensioned, so that when sailing close hauled in a brisk wind, the lee shrouds are tensioned and not loose. I use the method described in the manual first and then proceed to tension the forestay and then the port and starboard shrouds EVENLY, a little at a time , using the gauge, and then test the results on the water. Much better than guessing the tension by "feel".
Here is alink to the directions.
http://loosnaples.com/files/PDF/INST-02.pdf