Firstly, it appears I have two options.

1. At the first hopper fill opportunity, when the strike machine door is open, I spray the midget with nerve gas.

2. I find someone with a short skirt to play the machine for me.

Looking at this as a statistician, I couldn't see how it was possible to fix the hold precisely over any period of time.....

We must assume that the 'full sequence' of reel spins is completed when once the real jackpot (3rd line payout) is won.

Lets take this scenario: A new machine is installed and preset as you say, and play commences. Over a period of time, the reels spin so many thousands of times and the jackpot payout is approaching. In fact it is 7 spins away. The midget has his 10% hold and additionally is up by $1000 in preparation for the jackpot. The skirt sits down and inserts a $5 bill. The first 6 spins pay out absolutely nothing. The skirt only has 2 credits left and so plays reels 1 and 2 only. The red white and blue 7's appear on the third payout line. The skirt wins nothing. Does the midget think christmas has come early or does he know he has to 'adjust' the machine so the jackpot still gets paid soon?