NHWarrior ... I do know that the Kuryakyn 7418 wide chrome levers reuse the OEM hardware! I do recalll the adjust screw in the brake lever was very tight when i replaced mine some years ago. It's a M6 cross-pt screw approx 25mm or 1" long under the head with 1-nut. The control switch housings use a M5 screw for sure and i remember that the tap was too small for the Kuryakyn lever 
If M5 (0.197") is too small than it must be M6 (0.236"). There is only 1-thread pitch available in these metric sizes.
If the aftermarket lever you have uses US thd's your choices would be the following:
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3/16" = .1875"
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#10 = .190"
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1/4"-20 & 28 = .250"
Is it possible that the M6 screw was in the wrong bin?
If all else fails use the smaller screw with 2-nuts or the other option is to remove the lever from the MC and install the M5 or #10 screw with the head toward the MC piston using flat washers to set the proper length for freeplay and tighten with a nut before reassembling to the MC.