I hope someone else can help you with this question. I don't do tray develoment anymore and all of my data on TXT is out of date and of questionable reliability. However, based on projection I would think that you will need about 14 minutes of development of TXT with the 2;2100 dilution to get to a DR of about 1.6 thate would be suitable for pt/pd printing. This would be for a normal SBR scene.
Maybe somebody can give you more precise information. I actually have some new TXT in 7X17 size that I need to test and when I do I will make the data available.