On my end, RT seems to be fairly accurate....or at least good enough.
Two Steam 99S strung to 59 with Gosen Polylon 16 (from TW....not sure what type of machine they use), measured 54 on RT when I received them and before play. That seems reasonable enough to me for a cheap poly that has settled out for 2-3 days after stringing. I used the Gosen Polylon string factor thats already included in the app.
The same frames, after 5-6 sets of use, measure out around 44 on RT.
On the next stringing job, I am going to take measurements more frequently to see how fast tension actually drops off (i.e. does it drop from 54 to 44 after just a few minutes of use and hang out there, or is it a slow progression downward and then a plateau at 44).