I fished a lot at the start of the game and bought both the Small and Medium fuel tank upgrades assuming I could put them in in order - however, I was only prompted to upgrade to the Medium tank at the Customs shop. I have the Large tank now and have finished the stage 4 upgrades, but my fuel capacity still isn't at maximum. I also have only 4/5 for the Body Modification achievement - have I screwed this up my mistakenly skipping the Small tank upgrade?