Hi Andi
If you can reach the big pinch with your left you should be able to to keep your heel on no probs but here's some beta...
Tip ...place your heel carefully and point your toe into the crack kinda curling your toes round the edge a little
Tip... If you cant reach the big pinch use the not so good pinch place heel as above and then go into the pocket (this is the hardest move on two squirrels but me got it dialed now) then left to big pinch rejoin the lankmysters from here
Hope this helps andi , worth sticking with cos its such a cool problem