A mid foot cleat could be the answer for you. If I was going to try it I would find someone to drill new holes in my shoes. After that, the speedplays may be your best bet, especially since you can get pedals in differing axle lengths which may be part of the problem.
I know you've had several fittings, but I'm going to throw some things out there as possible issues, just in case something clicks for you:
Has anyone looked at your foot stance in terms of it potentially being too wide (most likely) or too narrow?
Are you comfortable in your saddle? Saddle discomfort makes you weight your feet more and aggravates the problem.
Has anyone assessed your spine/posture while riding?
Are your hamstrings and/or calves abnormally tight?
Do you have flat feet and have you tried a foot bed insert?
Can you unclip one foot and ride with one leg only without a dead spot at the top of your pedal stroke? If not, you might be able to help the problem by working on your pedaling mechanics.
Living life like there's no tomorrow.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS