I read about the controlled lamp upgrade for 3-7 boards, and that there are two options. One is replacing the transistor with a MOSFET and using 2 resistors per line to cut the draw down - the other is easier - replacing the transistor with a TIP-125(or 127) and adding in a 10k 1/4w resistor for the usually burned 27 ohm ones.

I've done it on Sys 6 boards without an issue, but can the same be done to a system 9 board since they're similar design/parts/etc? I see the mosfet option on Pinwiki, but like the TIP-125/127 solution better and would rather give that a go on the board.

Id recommend buying the switch blades and contacts from Pinball Resource and either remaking it yourself, or take a regular EOS, transfer it to the larger existing switch body, and add in the new low current pieces. I did this on my Firepower and its worked like a charm

Either way - PBR sells both low voltage and high voltage contacts and light/medium/heavy thickness blades. I fix a lot of EM/hugh current ones by taking a switch apart, replacing the contacts, and putting it back together.

Nah, so long as the open one makes solid contact, you'll be fine. Id keep the gap minimal, at least 1/8" but can be a bit more. The smaller the gap, the closer the flippers will flip together. 1/8th is recommended so the switches don't arc across.

Also, its important the closed switch doesn't open till near the end of the flipper stroke, or you'll lose power to soon in the shot.