Hey Bill, springs arrived today, the ones you found are ok, fractionally too long, but a bit of persuasion with pliers make it an excellent return spring.
the springs i found on ebay, although supposedly the correct length (65mm) , were way too long ... must be a problem in translation from mandarin ..
so #8 is nearing completion. awaiting correct fuel tap service kit from M&P... who have sent 2 incorrect kits so far ... finally spoke to a human, and problem is now resolved (well, not got me money back yet.... but i live in hope)
cheers