I use a golf peg/tee, screw etc to cover the fill line and some models. On some I use proper purpose made pop in/out metal filling points. Some have valves on them to make it neater etc. You can also buy purpose made plastic pinch things.
eg
http://www.radicalrc.com/shop/images/101359.JPG
http://www.radicalrc.com/shop/images/101992.JPG
Fuel filters, yeah one on your pump and one between tank pick up and carb is fine. Nothing will get in if you keep the lid on the fuel. I always have a filter next to the clunk on the fuel pick up line from my hand pump or electric pump.
Make sure there is lots and lots of foam sandwiched between fuel tank and sides of tank. To stop any movement at any angle.
Also the pipe in your fuel tank that wil be bent upwards, make sure it is pointing upwards.
Also the clunk inside the tank (fuel pick up line) make certain it cannot kink and is able to move around the inside of your tank unhindered. Very critical otherwise dead stick time as soon as you change pitch. If the clunk gets caught on anything within the tank.
As for your hinges whatever method you go for, think about putting cocktail sticks or small brass pins straight through the control surfaces and hinge and cyano them in and snip of to make neat.
Just makes your hinges 100% secure. Just in case!
One other thing just noticed on your photo, I may be wrong here but it looks like there is no glow plug in the engine? if that is the case, get one in and cover that hole. Any crap gets in there could be bad for the engine.
Have you got your spinner yet?
Something to start it with ?
Also do you know how much 'throw' the control surfaces need ?, what pitch prop for that engine?
I would also reccomend adding some exponential around neautral on your Tx as well, especially if you are starting new.