Put a meter on the wires to figure out what is what if not in the manual.

Only thing that optos might make hot is if they are dirty and slightly closed. Since you don't have optos in there now, I'd check for worn parts, binding parts, a tiny bit of up and down play on the flipper shaft.

LTG : )

If we can trust the manual, it must be something like this:

wiring flpbttn.jpg

The colors in the manual that zaza posted are correct. You have to wire all wires to the board, as the right board is connected THROUGH the left board.

Also - for the overheating - no, the optos wouldn't cause just the high-power to be active. They just signal the flipper board when to activate the coils. Dirty optos COULD cause the transistors to leak which would cause them to get hot - but if they're hot with leafe switches, then a transistor may just be leaking.
You can tell if the Hold coil is active at all by manually trying to push the flipper down - if you do, once the EOS is opened, the Fliptronics board will re-activate the power coil, and you'll feel it.

You have other issues going on there. Wrong coils ? Wired wrong ? somebody converted to pre fliptronic flippers ?

Your game is fliptronics - EOS switches are open when the flipper is at rest.

LTG : )