msd 6 install questions

[GhettoPop]

installing an msd 6a and blaster ss coil in car in sig. i want to mount it on the driver's side fender brace behind the battery, on that 6 inch piece of metal with two 8mm bolts on it, on the front driver's side near the horn. is this a good spot or can water be a problem here?

questions for the electrical hookup for the msd:
large red wire = (+)batt terminal or (+)starter solenoid? which is better?
large black wire = (-)batt terminal or ground elsewhere? which is better?
orange = (+)coil
black = (-)coil
red = switched 12V source, whats a good source?
white trigger wire = whats a good source?

any specific wires that are good to tap into would be a big help

magnetic triggers:
violet
green

i know that i dont need to use the magnetic triggers, but i wanted to set up a kill switch for the msd. can i simply extend the violet wire, attach to a switch, then from the other end of the switch run a grounded wire? when the switch is open and the msd's violet wire is grounded. i believe this will safey disable the msd, causing the car not to start. make sense? can this cause problems?