I know what you're looking for. I could only find 12mm hex extensions for 5mm axles (Slash/Stampede). I couldn't find anything that fits a 6mm axle.
I run 2.8s on my EB48. I had to remove a minor amount of material on the corners of the carriers to make it work. Maybe that will work for you?
If you use EB48sl 17mm hex conversions on your truck everything will work. This is assuming you're using Proline wheels. This is how I ran my monster SCT410.3 and it worked perfectly. A byproduct of this setup is even on 4s you'll never strip a wheel hex.