Mordib, Looked at your picture to lower tank. I cut out 1/16 ply both bottom and sides. Did you cut another round fuel tank hole just below motor mount in firewall or did you just make fuel tubing holes? If you just made tubing holes one would not need to cut the ply out! If you just cut the upper bulkhead brace out, long saw, stand on your head etc. and insert the tank it will fall in line with the lower bulkhead crossmember and you can push the tank in, then back , to rest on the former foreward the landing gear mount. Yes there is some extra fuel tubing from the further aft location however I do not think it an issue. This would negate any cutting. I will run and fly the plane to confirm if an extra inch of fuel tubing, with a correctly mounted tank makes a difference. WHMC