Testicles slipping out and burning sensation inside the sac

I’ve been using the CB6000s for several months now. I began with the second largest ring (the kit includes five rings if you’re new to this). The issue was that my testicles would slip out quite easily, sometimes even while driving. So I switched to a smaller ring size. Now, during workouts, they occasionally pop out again. This is actually quite painful because of the tighter fit. Deciding to go down another step in size, I’m now on the second smallest ring available. There’s no more slippage, but I wake up several times at night and also upon waking with a sharp burning feeling under my scrotum. I tried enduring it for a week, but it doesn’t look like it will improve; if anything, it feels worse. I’m using the smallest spacer that comes with the device. Most of the time (95%), my testicles sit high and tight. I’ve done some reading and see many folks prefer the Holytrainer models. I know I can get custom-sized rings, but I’d appreciate any advice on dealing with both ball slippage and scrotal burning, as well as tips for sizing up or down before committing to a new device.