For either case, I suppose I would recommend hogging out the hole for the 1/4" jack and going to a 4 pin XLR jack instead. You simply need to wire the jack appropriately, which will split your grounds for you. You'll want a pair of resistors for each channel to go from + to ground and - to ground. These can just be 100 ohm resistors (wattage isn't important).
Often times the 4 pin XLR jack has a ground tab. Since the SEX is transformer coupled, it's completely OK to run all four of those resistors to the ground lug on the XLR jack since it's convenient.
One day there will be a 1/4" TRRS jack that will make this easier, but for now this would be my recommendation.