Drop is related to time of flight, longer it takes to get to the target more it drops. If not much a little increase in velocity will help lighter bullet will mean higher velocity.

But I like Black powder velocities and would recommend altering the sights.   Which way higher rear or lower front depends on what you have to start with. If the front is high filing it down can make a big difference

Might take the front off and put a plastic throwaway sight on with duct tape or zip ties. Then cut it down to zero.  That will let you see what the proper height is without any calculations. Depending on your rear sight can do the same simple riser block out of something easy to cut and shape, longer screws see how it does. Then make a permanent riser.

Boats

Is the setting shown on your rear sight the one you're having problems with?  It's shown at the lowest elevation...if so, raise your rear sight to get to what you need at 200 yards.

David

Ok, so with the sight at about 10% to 20% up off the bottom setting, where does it hit at 100 yards?  Shoot a group at that distance and find the group center on paper.  Measure from there to the desired point of impact.  Measure the sight radius.  Multiply the sight radius distance in inches by the amount of correction in inches, then divide by the distance to the target in inches...100 yards being 3,600 inches.  This will give you the total amount you will have to move your sights to get you dead on at your 100 yard base distance, with a bit of down movement available for fine tuning if needed.  So, you'll need to lower your front sight, or get a lower one by the approximate amount you compute.   

David

Fergot to mention, when you're shooting your group for measurement purposes, hold the sight picture you intend to use with the new, lower, front sight.     Even if that means a taller piece of target paper with the aiming point near the top.

David