I too have no experience with Tri-X, but I've been using PMK with Ilford Delta films for about a year. My practice has been to cut the ISO in half (as you have done) and then take about a minute off the sheet film starting times that come with the PMK kit from Photographers' Formulary. I use the printed times for roll films (and would try them for sheets, if I used sheets.) Results are lovely.(posted 9427 days ago)