In reply to Lee Mac:
Great stuff, thanks.
I was trying it as I described today, but shredded right hand put an early finish on my fun.
I'm currently doing a SDS with hands as per UKC info and left foot in chalked pocket in roof. I pull on and stick right heel against Jack's Arete bloc with right toes cammed under bottom left corner of Mango/Sheriff bloc. This allows me a couple of slaps up the arete but that's as far as I've got - being able to move the left hand to an intermediate may just unlock the problem for me. Will have to wait until the next dry spell, hopefully at the end of the week.
Thanks again