Just checked the Diana and TX to my surprise the Diana is OK except a really tight choke this explains the power lose with the green exact's even though no loose spots for the air to go around the pellet like the .22 80 with the loose area in the middle of the barrel.
As expected, the TX was fine even with the dreaded greens.

You need the greens to test as they don't deform when pushing through but keep their shape in the loose spots where they have been resized by the tight spots.

So I might give the .177 barrel a go on the 80, I did the crown with the help of Mick and others with a ball head screw some time back and have not tested it yet so will be interesting in more way than one