As per somebody's advice, I tried incorporating some light transparency. I decided to do this with water, which makes no sense when using a gas tank, so I decided to rectify that with the text tool to maintain my usual level of professionalism.

The success was only limited, really, but I think it works alright. It doesn't stick out too much - the optimal line of thought upon seeing this would probably be something like seeing that she's straining from being too full, and then so full that she's beginning to show through. Something like that, I guess. I'll have to toy around with it some more.