Thanks for all the contributions guys. It's good to see a few different opinions. As a person that has studies physics I too think location should not matter once the plane is running however starting the plane is where my problem lies.

even if I wanted to lower the tank it would not be possible as there is just nowhere for a new bung hole. Even if I fill the old one and reinforce the firewall.

anyway going back to the debate above. Great debate by the way chaos. Would it be acceptable for a centre line to be lower than spray bar then? Surely the muffler produces enough pressure to push the fuel through?

As fas as my pc-9 goes I got it in the air. I had to fuel up, keep e throttle at closed off and right before starting I set to idle. I also removed the plug to check it was dry. It actually started quite easily to be honest. It did cut in the air and I had to dead stick. Wow these planes come in fast.

I refuelled and checked the high end needle again. The low end is pretty good with smooth transition. I somehow set it too rich and only noticed when airborne. Came in for a landing straight away and set down fine but hit a bloody goal post so now got a leading edge crunch and wing mount bolt holes to refit. No big deal really.

I think the centre line alignment won't do any harm to follow as a rule but if it's so important surely he manufacturers would factor this into the designs and plans. On most of the planes I've seen it comes through the centre of the mount. Well that's never going to be in the right place so seems daft.

I'll repair the plane and let you know how I get on.

I've just bought a travel air from black horse with an Irvine engine and servos for £20 ($30) it meads a repair to the tail plane but only minor. Engine is upright so at least this will be easier.