Actually pressure is not truly your main concern with the Flues. Shot weight vs velocity is. 1295 FPS is in my opinion too Hot for the flues, even if you can keep the pressure down. If this load has 1 oz of shot then that is a 3 dram equivalent powder charge. Looking quickly at an old Hercules handloading guide I can find a 1oz load @ 1290 fps with a PSI of only 7,400. That pressure is not too high for the Flues, the load itself IS.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra