Okay, latest update on my experience with my Campagnolo Pro-Fit pedals on another long ride (65 miles over about 4 hours, no breaks longer than a minute or so). This was after moving the cleats back a little, after my previous experience. This sportive was much less hilly, though the strong headwind for a lot of the ride was really energy-sapping.
Anyone, as far as the pedals felt, this time they were fine up to about 20 minutes miles, when the first tingles started, then the ends of my feet started to progressively a bit numb (don't think due to cold, had toe covers and (thin) thermal socks on and it wasn't that cold). The numbness actually didn't get that bad and was bearable, BUT after around the 45 mile mark I had a similar experience to last time, started to feel like there was a solid bar perpendicular to the sole pressing into my feet, just behind the ball of foot. This really wasn't nice to ride with, had to point the pedals downwards on the down stroke to try to minimize the pain.
I was wearing Specialized Torch 2.0 shoes with carbon soles.
I'm sure alot of it is probably down to cleat position, but I'm finding it hard to get this right, if this is what it is. Think I may try some (new) Shimamo 5800 SPD-L pedals I picked up cheap recently, to see if they're any more comfortable. I can already tell that the bearings are not as nice, though and am concerned the release tension may be too high for my liking/safety, especially when tired near the end of a long ride.