hmm i must be confused.. i was under the impression that wire that tapped into the alarm wire from the pin swtich was just part of the "set off the alarm when this circuit is grounded" (or however it works) circuit and the actual disarming of the alarm came from using the unlock button on the remote, i used the door unlock relay for mine, but i remember the rear door solonoid being on a seperate circuit from the alarm


edit
ahhh! reread your post.. we are on the same page... my concern is that by using the 'option' button on the remote to activate the solonoid, the back door will open, but unless you hit the 'unlock' button the alarm will still be active, b/c as far as i know 'option' doesnt disarm the alarm
.. i think