How to program HePSU negatives

So after about 6-7 months of working partial ROM HePSU, I've decided it might be a good idea to change the stimulus and start doing negatives. The problem is, except for pull up negatives over a year ago I dont have alot of experience with them, and so not much idea on what kind of set/rep range would be best. Right now I'm doing 5 second negatives as close to my best effort. Any ideas?

Thank you,

Amebix

Same thing as any, 3-5. I find 3-4 taxing enough especially if they are longer than 5s.

Haven't worked them in a long time.