I have no idea what the GTX feels like, but I do have a few examples of the T05 Diana trigger, the one with one screw. Turning the screw counter-clockwise will lengthen the first stage and lighten the second, just turn the screw in 1/4 turn incriments 'til you are happy. If you turn the screw to far out you will not be able to detect the second stage, so you'll need to turn it back in a bit 'til you get a safe second stage.
My first Diana was a 24 with the same trigger as your 54, and with adjustment and continued use it just gets better and better IMO. After about 1000rds I actually had to turn the trigger adjustment screw back in a bit as I felt it was getting to light in the second stage. Have fun and I hope this helps.
Mulby