a good ground can be check with a dmm, As with the ground run up to the main batt, you can do this if you serious pulling some rms. I Just have big three and have 2 grounds that will run to batt in rear. They are connected to strut towers and paint has been sanded away. i had no issues on 1500rms stock alt and big three. All wire is 2/0 knu. I went and up my rms to 2500 and now have seen voltage drop. thus i orderd batt for rear. OP just make sure your ground is secure and used a bolt, i repeat make sure its a bolt not a sheet metal screw or the seat frame bolts.