The length of your tailpipe from muffler back matters a lot to the rpm where Drone is most severe. Just as a Church Organ makes different musical notes when different length pipes get air blown through them, so will your exhaust make annoying music.

Very roughly, if drone was severe at 2000 rpm, and much less at 1500 rpm,
then your tailpipe length needs to increase
2000 divided by 1500
4/3 rds

Other things come into play here, such as the temperature of the exhaust gas, which will be higher the more the trottle is opened.

You could experiment to find the added length that snuffs out drone.
Buy two ninety degree fittings, and two lengths of either solid or flexible corrigated pipe,
and add maximum length for side outlet style exhaust,
then cut off about two inches at a time untill the exhaust note suits you.

Drive up steep hills to demonstrate how a more open throttle changes exhaust temperature and therefore drone.

The quietest set up for low drone in the 1200 to 2200 rpm range is usually large "Helmhertz Trap" mufflers mounted cross ways near the rear bumper fed by as long as possible tailpipes. T-Traps of closed stub pipes the right length can also kill drone at a particular rpm.