Chad,
Basically, this is what the 5 terminals is for (on most Cub Cadets):
-1 terminal is to connect to one positive wire to PTO clutch (the negative of pto goes to ground)
-1 terminal is to connect to a fuse (then to ignition switch)
-1 terminal is to connect to a safety switch (then to solenoid)
-1 terminal is to connect to the ignition switch
-1 terminal does nothing
I believe the 5th terminal is for another PTO engage, which is what you have in your case- 2 electric PTO's. So, a single setting switch might have the 5th terminal do nothing.
If you can identify each wire and where it goes, and match up to the terminals of the single setting switch, then in theory it should work. After all, switches are simply a device that interrupts the circuitry.
In the case of your PTO, you probably can get away with a redneck job- this is to put the original switch, still connected, behind the dash... Splice in a 2-terminal switch to the 2 wires that matters for your deck PTO and hook the 2 terminal switch to the dash.
Personally, I think if you love your tractor enough, and plan to keep it for years to come, the full price is worth it. You might need the front PTO in the future anyway?
Hope this helps.
Sincerely,
George