Re the seam on the tank...Not sure if you have painted the tank yet, nor whether you intend to. But I am thinking it should be possible to "fake" the seam in question by tacking a carefully made one on (BigOz springs to mind)....A bit of crafty blending with filler and you'ld never know..
HA ha ha I've put the idea in your head now.....Bad Gazza...
