Maxb,
I'd cut another servo opening next to the existing one or just route it from the other side servo hole. If you install a choke servo you don't really need the optical kill switch.
Solder a battery connector it the ignition module and then get the Cermark switch with the built in charge receptacle. You'll want to be able to check the status of your ignition battery without removing the hatch. Definitely move the tank over the wing tube and use a 16 oz tank. I have 1/3 left in the tank after a twelve minute run.

Aeromodeler,
Do a search and I think you'll find opinions are 50-50 on soft mounts. At our field I have seen 7 Patty's and zero soft mounts.