What's the modification to make XJ AW4 run in second gear? (Miller, you there?)

I remember years ago Miller had said something about cutting a wire under the passenger dash and installing a switch. Will it shift 1-2 after this mod or start in 2 and stay there? I want to do this before Oscar. Thanks!
Installed a single pole double throw switch to power the 2nd gear solenoid from a wire that is only hot in 1-2 on the shifter. Worked good first day of Oscar in 2018 then blew the 7.5 amp trans fuse under the dash. (Thanks, Larry, for a new fuse) Bypassed the mod for the second day at Oscar. Yesterday I ran a wire from a terminal on the fuse panel that is hot with ignition on, through a fuse holder with 5 amp fuse, through the spdt switch and it works fine. Now I'm concerned about what will happen if the shifter is moved out of 1-2 (operator error) without putting the new switch back into the "normal" position (ie: the 2nd gear solenoid could be energized in neutral or reverse) maybe I need to engage a relay with the "hot in 1-2" wire to complete the circuit from the "hot with ignition on" power source. I'll give this more thought. Anyone have any input on this?