I was curious as I just got some hemp oil that I used in lotion and it's lovely stuff. Playing around with soapcalc, I got some nice numbers using 20% hemp, 25% CO, 35% PO, and 20% OO. Linoleic and Linolenic acids combined were at 22, a bit higher than the regulation 15 but not too bad. If you used ROE or vitamin E to retard oxidation, I think you'd get a reasonably stable soap at 20% hemp. You might even push it to 25% but I'd hesitate to go beyond that.
Hmm, I think I may give this recipe a shot myself.