As for adjusting cathode length, the silvertron instruction sheet suggests maintaining >10v throughout the process. With electrolyte in the mix I generally only have about 1/4" of cathode submerged to maintain >10v.
Between reading your last post and watching the progress of the electrolyte-free batch I started this morning, it's apparent that the conductivity in an electrolyte free batch never gets high enough in a 20ppm run to drop the voltage below 10v.
Unless for some reason I want to make a batch in a hurry, in the future I'll likely skip the electrolyte.