Well, I did it!
Really happy with how the 6mm tunnels look!
I used the Black Glass Dead Stretching Kit from Stretch It Body Jewellery and would definitely recommend it. No pain and small 0.5mm increments.
I may end up going to 8mm in the future, but do really like the subtle look of 6mm.
Update: I did end up going to 8mm. Super happy with this size, as the hole is less subtle but still keeps my ear looking like a normal ear shape. I also bought a load of ear plugs/tunnels, so I’m very much invested in this size. 😄