I am using Slic3r. I don’t see why internal dimensions should be smaller. I take it you’re ruled out a slight over extrusion.
I have printed a z-lower with my e3d v6 to check for dimensions, and the bearing was a perfect fit, so I’ll be in a position to see about internal dimensions once the volcano is dialled in enough to try it. Pics and settings will be posted following that.
I have a feeling 0.8 will be too far, and expect to find the sweet spot at 1.0mm nozzle and 0.6mm layer height. Nozzle temperature was going down a bit at times with that volume of PLA pouring through.
I found out about Volcano before MPCNC, so when I recalled the claim that parts are stronger, I was keen to try it out.
Initial impressions of the parts is that they are harder to break, but perhaps a tiny bit less rigid. Perhaps a little less brittle, but I don’t know if any lack of rigidity would be an issue.