The ABS 20mm test part file that came with the CTC Rep dual separates from the raft nice and clean - with the bottom looking nearly as nice as the top.
In testing my designs, the base of the part pulls away but leaves a rough surface which would need to be cleaned up quite a bit with sanding. The temps and speeds used are identical to the test part.

In subsequent builds, I have raised the part off the base/raft from .2mm to .8mm, then used "supports" and still not much has changed.

Any tips in part design to get a smooth base to separate like the provided sample?