I was just about to answer about the coils and you beat me to the post!  I think because the right ramp feels close the left flipper needs the weaker coil, but the shot to get it up the left ramp (when the flap is down) to enter the whirlpool needed that extra grunt.

I have worked on 2 creatures and the first one had the metal rails and the one I have now has the wood, not sure why or how they decided etc.

I remember seeing the treasure cove proto with the  86 bulbs sticking out the top of the ramps, I had forgot about that until you mentioned it.  Like you said John, it would have been far easier to change them!

Oh and I thought that the Amber caps may have been the proto colour, seems not!