fuel tank orientation

I have done it many times. Just make sure the vent tube is not obstructed. I usually notch the end of the tube so that can't happen. The LHS stocks tanks that made wider than tall but they aren't always in the right proportions.

I'm not sure I understand what you mean by "header change". The needle valve settings will change when the clunk height is changed either lower or higher than the needle valve.

I vote no. If your fuse is wide enough, go for it. However, I don't think it would help fuel draw much. MHO mk

Fuel tanks may be put in any advantageous position, as seen in pusher aircraft, ducted fan aircraft, turbines and boats with multi tanks, but may need a header tank or pump. Refer to: "Fuel facts & FAQ + Fuel Tank installations" on my web page for various set up. regards Alan T. Alan's Hobby, Model & RC Web Links

A/ Perhaps I wasnt clear. When the tank is say an oblong shape does it matter if the narrower part is vertical or can it be put on its side. If the latter, then does the engine see a lesser change in fuel head relative to the needle valve. If this is true then it would stand to reason that all fuel tanks would be better this way round.

I learned how to properly adjust needle valves from George Aldrich. One of his 'tricks' was to do all the adjustments with the tank 1/2 full. He did it that way to adjust for the low fuel high fuel situations. I doubt it will have any impact on the fuel draw, but it will make the change in richness less dramatic.

I thought it may be better half empty, but I'm a pessimist!

Opps. sorry couldnt resist that.