I tried the 145X in a 22" 1:10 twist Marlin X7 and got horrible accuracy, but since nobody has offered an H1000 load, here's the two I ran.
No pressure issues, and likely a little room to grow. With H1000, I achieved 2980 easily with a couple different 140 grain bullets, and 2935 fps with 150 grain bullets, so I'm guessing there's another grain or two to go with the following charges.
Not sure why the half grain seems to have had little affect. The two tests were a few weeks apart, and these were shooting so bad, I didn't bother recording the details and gave up on the 145X at that point.