The second method, absolutely. I had the exact same idea as soon as I started reading this. You are asking for trouble if you start drilling into the side of the IP. The screw you are referring to is indeed the full load screw. Make an L-bracket with a thru hole and sock it down with a nut that fits onto the full load bolt. Obviously, the other end of the "L" gets a threaded hole to receive the idle stop screw.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.