You might take a look at this article on low pressure 20 ga. loads. It addresses at least one of your powders.
http://www.nssa-nsca.org/wp-content/...R/cerettos.pdf
Hercules (1990) manual shows a very low pressure load, but not one of your powders:
3/4 oz. CCI 109 RXP20, or WWAA20, 17.0 gr Unique, 6,800 psi, 1200 fps - Federal paper case!
Ron