I understand the skepticism about GTA but it works on Ridder almost without fail. The issue with that spot near old Plains OP is that like blu said it's a long walk if you don't have lugz rez. It would be ok for a large arranged circle with lots of rezzers on both sides. Otherwise not very practical. Also, remember no matter where you spar the moors is an open zone so regardless of where it is be ready to die if you spar.
Brandywine: Immanitas R12 Burg, Sueahpro R11 Mini, Falsified R9 RK, -The Blood Hand
Crickhollow: Orphluk R9 Warg, Orphelun-1 R8 RK. -The Blood Hand.
Landroval: Gorbat R12 Reaver.