I printed a raft plus two layers of the polymer pump before I went to bed last night. This time the raft was very solid (95%/30%). The first two layers went smoothly. At the third layer it became apparent that I had the layer thickness a bit low for a (95%/27%) flow rate, so I jacked it up to 0.67 from 0.5 mm. I kept fiddling with the layer thickness for layers four and five and finally abandoned the print after I managed to do layer five successfully but too messily to suit me.
I am going to let the print that I just did cool for a few hours to see if I get any warping or curling. So far there isn't any corner curling at all, but you never know. After that I will try a new print with fixed settings this time of 95%/30% for the raft and 95%/27% for the pump with a layer thickness of 0.62.
The pump will have 21 layers at that thickness. I'm getting there.