In either case, whether using the tube in the ear or with the modified steth, the gas flow rate is very slow (max 1/8 lpm). With either method, you will smell a little bit of ozone when doing the protocol as it leaks out the ears. It is practically unavoidable, depending how long you are doing the insufflation. When it gets to the point that you feel you're breathing too much ozone, then stop the treatment.
You can "unspring" the steth by bending the centre spring so it is comfortable to wear and provides the optimal pressure to both ears. You have to have some pressure in the ear or the treatment will be worthless. The ozone simply will not work well if there is no pressure to drive it into the ear canal. It's all about finding that fine balance of flow rate, concentration and pressure.
Hope this helps,