Kinda depends on your sight picture with that specific target - lighting plays havoc with groups sometimes - tight, round groups are what we're all after. Elevation can be caused by differing pressure when seating the ball on the powder. As the barrel heats up, heat waves play havoc with a group. 1 1/2" isn't too bad if it's 50 yards or farther, especially with such a light load. Too - are you wiping at any time during the group? Do you have to wipe during a group? Can you shoot 30 or 40 shots without having to wipe? Are you shooting at 50 yards? Offhand or benched?
I believe 70gr. of 2f is a very light, squib load for a .54 - it's too light for a .50 in my book. Try increasing your charge to at least 85gr. 2F - maybe 90gr. to 95gr. and see what happens. More powder is needed for longer ranges. Guys I know who shoot well at long range with .50's and .54's, ie: 75 to 200 yards, are using 120gr. 2f in a .54. larger calibres use even more powder to get accuracy at the longer ranges.