Very nice work, looking good so far.
Magnu is partly correct about the flaps - the 'hinge line' was not painted, and should be bare metal (not polished alloy, more a steel colour). You'll find two oval indentations on each hinge line, and these were open slots giving access to the hinge arms themselves. The 'silver' coloured drop tanks were the 'paper' ones, and were finished in a silver dope which, although sometimes exhibiting some shine, weren't highly polished or as bright as the metal 'tear drop' tanks (these could be bare metal, or silver painted. earlier versions were Neutral grey or Olive drab).
Those tanks which were the same shape as the 'paper' tanks, but painted Neutral Grey, were the metal 108 gallon variety. The 'at a glance' identification feature is the ribbed 'nose' of the tank - the metal tanks were smooth, the paper tanks had the reinforcing ribs.