The problem with doubles is the barrels are converging not parallel so solid ball do cross over at some point. Question is when and how far do they drift apart down range. If they cross at 30 and are six inches apart at 60 you could use that type information to adjust your hold point to get decent accuracy. You are limited to simple bead sight and can not expect single hole grouping at 75 yards but you should get decent results to 50 yards. Your hunting to be with family not put meat on the table to feed your family so you can always be selective.
We use to use a paper plate as a target at 50 yards and knew if we could hit the paper plate it would be a fair substitute for a deers vitals. So as long as we could reliable hit the plate we were good because slug energy was never the issue just accuracy.