Believe one of the main purposes of doing negatives was the very slow and controlled lowering portion of the lift. And to use much more weight in a true negative/eccentric rep. We are all much stronger in the negative than the positive range of any lift.
Art Jones approved. The great Marvin Eder (and others during that era) favored one arm DB negatives. And, if remembering correctly, applied negatives to chins and dips. Recorded over 400+ for a full dip, at one time. Also overwhelming strong at any form of chins, one arm included. (one arm chins do respond very well to negative training...of course right along with the normal positive version)
If ever getting seriously in negative training, you will probably need a training partner(s). Like anything else, this form of very demanding training is not designed for everyone. A short training cycle of 4 to 5 weeks max is advised. Should not be a regular exercise standard for most folks. Good Luck.