Since you brought this up, what are the ballistics you used for that slug? Is it the normal 900fps to 1,050fps of a 3-4 dram loaded 12 bore Paradox?

Even at the figures above, there is 1 1/2" more climb at intermediate ranges than I will allow for my own shooting. Compared the figures below, there's over 2" too much climb, destroying the point blank shooting - for me.

When I ran the figures for the paradox guns I've read about through Seyfried, I see something slightly different.

These figures are for a 12 bore - 10's and 8's have considerably more rise and drop.
30yds. + 3.53": 50 yds. + 4.54": 70 yds. + 3.94": 90 yds. 1.75": on at 100yds: 120 yds. -4.76": 125 yard -6.23 - fine for broadside standing shots - I prefer flatter shooting.

As you can see, there is no point blank range for this rifle at all, where a shot coult be taken at the forehead of a bear of buffalo with any certainty of where the bullet would hit. The point blank, of course is the range where no allowance has to be made.

Each to his own - I acknowledge slugs finally overcame the round ball. As indicated, it was due to being able to use hardened slugs to allow sufficient penetration, which, before hand was inferior to round balls.
The lightweight parodox guns were meant for shot or ball(conical ball), and were not built for the heavier loads that actually gave conicals better results on heavy game than round balls had provided prior to this.
Paradox's are great - would love to have one and to hunt with it, too - but - I would also try it with round balls, just to see if it would regulate at higher speeds with the lighter projectiles. You see, round balls penetrate just fine - "both sides of an elephant's head"(Baker's words) is good enough for me as I relish in their flattness of trajectory over the normal hunting ranges I shoot bears and moose.
With a 100 yard zero, a 12 bore RB would have:
25yards + 1.32": 50 yards +2.29": 75 yards + 1.93": 100 yards 0.0": 125 yards 3.74": 150 yards -9.47": approximately, the 750gr. paradox slug noted above in the table would not overtake the ball's trajectory untill well past any likely range such bores would be shot at - ie: not until the ball strikes the earth due to past maximum range. Indeed, the Round Ball is flatter than the paradox conical at 200 yards by 15.01" and the difference gets greater out until the ball strikes the ground - somewhere around 800yards or so.

Now, increase that Paradox conical's velocity from a normal 1,000fps to 1,400fps and it's a world different and actually beats a round ball past about 140yards for trajectory as they are equal in drop at that range ony. At midrange to 100 yards, the round ball has a very slight advantage in trajectory over the faster stepping slug, and at 140, they are equal.
Of course, at any range, the harder, fast moving slug will penetrate more deeply than a hard round ball, but how much is necessary?
How much does a 750gr. slug moving 1,400fps kick, when propelled by black powder? Can 1,400fps be safely obtained in a 7 1/2 to 8 pound 12 bore Paradox?