I pulled it up. First of all I don't know why a mechanical/manual tilt bracket shortening would be part of it. The tilt bracket is for locking the engine in the up position when pressure is not desired on the PTT to hold the engine up....not to be used in trailering as it may be too fragile to tolerate road bumps and all. A LU to trailer bar, separate after market item is used for that.
The mercury switch is a ball of mercury that rolls around inside a sealed glass envelope. Included inside the glass envelope are a pair of contacts which the ball shorts out if you tilt the appropriate end and opens in the reverse. Accuracy is somewhat questionable. Your whole tilt range is like -4 to + 15 to 20 out of a 360 degree circle. The difference of a couple of degrees could make the difference between hitting the cowling on the boat, and not being able to lift the LU out of the water when moored.
That switch is naturally grounding something through the mounting bracket (and having only one lead) when closed. Question is What? You can't put it in the PTT control or power ground as it would affect both up and down equally. Once you tilted the engine up the switch would open totally disabling your PTT motor and you couldn't make it come down. What you want is an isolated (from ground) series switch that you can put in the blue line (12v when going up) that opens that circuit when tilt reaches a certain height. A SPST of the type I mentioned is much more accurate (opinion) and if you use a slotted bracket you can tweak it to exacly where you want it. Accuracy on that depends on the spring inside the switch and that would have to be tested to be determined. A sealed switch would be desirable in my thinking this through and such is available.
The Mercury switch may be a better solution since it's naturally sealed, but you don't want one that grounds. You could use the switch you mentioned if you isolated the switch from the bracket and attach a separate lugged wire to the the insulated screw (like nylon which is readily available) and touches the switch tab which is now under the metal screw. To complete the installation you would need an insulating washer between the body of the switch and the bracket shown; anything plastic, rubber, or mica are options.
Since you are looking at a hundred bucks here on the switch you mentioned, and would have to do the mods mentioned to do what I think needs doing, surely you can get what you are looking for with a little digging around for around $20. However, if you cobble up your own design, the question still remains as to why the shortening of the tilt bracket?
Stay in touch.
Mark