You REALLY don't want it to grab any harder. Drums have a nasty habit of locking up under super aggressive breaking. The best way is probably to adjust them until you feel comfortable hauling really hard on the binders, or going to a different shoe compound, but the selection is rather limited. I know that's a bit vague. but seriously, you don't want them to lock up. Also, try getting used to using both brakes to stop. It's somewhat counter-intuitive, but learning to use them both significantly improves stopping.