As long as you can vent the pressure off of the tank as you fill that would be great. Just watch the tank as you fill and make sure that it does not balloon up. There is a good chance that it will. Its a great idea, IF it works.

As far as component upgrades, in the grand scheme this is a pretty small plane with minimal electrical load so there in not much need for upgrade. Standard extensions and switches should be ok. You might upgrade to a HD switch but I dont think its really necessary. The real place to make this plane stand up and dance is in using the right servos and minimizing excess weight. The smaller the plane, the more critical the small weight savings become. Going with Lithium batteries although not necessary is a good upgrade and a way to save a couple of ounces. Also going with a higher Nitro fuel will make that Saito really come to life.

High speed digital servos would really make a difference. Something like a Hitec 5945 or even better 5985s on the control surfaces would make a big difference. I would not use the 5600 series servos if you really want optimal performance. They are ok, but they are a little slower and a lot sloppier. The 5900 series servos really do make a difference. That or a JR/Futaba equivalent servo like the 9350.