Unseau, You are going to enjoy building the Sig Ryan-STA. I built the same model in 2012. Here is the link to my build thread, I think you will find it useful while you are building yours. It should answer most if not all of your questions or concerns.
http://www.rcuniverse.com/forum/kit-...-ryan-sta.html
I chose to install a DLE 20 gasoline engine in mine and while I did have to make alterations in positioning the firewall, it fit quite well. In selecting a gas tank for this model make sure that it is for gasoline and not for Glow fuel should you decide on a gas engine. Tanks specified for Glow fuel can be retrofitted for gas by changing components such as o-rings, etc. that would otherwise be ruined by gasoline. A small tank can be used as gas engines are very economical. Positioning the tank in relation to the engine isn't necessary, as these engines have fuel pumps. If you need assistance I would be happy to offer my help.
On
page 68, post #1685, you will find a complete list of specifications and components that I used.
Happy reading!
VincentJ