First off the fancy plastic cap on the Dreamer is crap and screws up the use of thermocouples.

It is a "MK10" setup. I had some worn out nozzles from Micro Swiss and I drilled them to .6, it worked really good. Probably could go up to .8mm but you will quickly start running into the nozzle design not being able to keep up with the amount of plastic needed at higher speeds.

What do you mean the PTFE tubes wouldn't fit? They should already have PTFE in them.