Suggestions for muscle car sound muffler without drone

This is sort of strange but I'm running 3" with X pipe and UltraFlo's dumped at the axle. I haven't noticed any drone thus far with them. I expected some but nothing yet. Possibly because they are still new? I do have some Fat Mat on the floor so that may be helping. The floor isn't 100% covered with the deadener. I installed it in patches.