[O.B.Left]

to get the feeling of extensor without tension, i pump the arms at address slightly bring both in a little with soft elbows and then gently stretching the left arm taught with right tricep/#3 making sure the stretch direction is below plane, it's easy to get tense and locked up when really focusing on extensor but it should do the opposite, it should eliminate tension so give the arms a little pump and you might find extensor a little better

Have you tried using #1pp? Although EA doesn't move the left arm the #1 pp can still be employed as the pressure point associated with fanning and bending , RFT. Making it a dual purpose pressure point during the backswing. Lynn does this. Simplification is a good thing.