When I use sugar in a rub, I never use more than 20% ratio. I've seen many rib rub recipes that call for over 75% sugar! And when I do use sugar in a rub, it's always turbinado. I save the brown sugar for any sauces I make.
Just for kicks, you could try using SPOG on your ribs. It's shocking how well that works on anything.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)