@tnt: That led me down a bit of a rabbit hole. I had added the capability to specify a delta for a parameter value like length some time ago, but in the end I didn't use it, so it hadn't been thoroughly tested. Of course it was broken (the scalefactor got lost between the .ext file and the .spice file). So I have updated magic to version 8.3.441 now, which fixes the scalefactor issue, and I will push an update to the sky130 PDK tomorrow with the correct offsets on the resistor length.