I hear you about nit looking 300 it's the biggest problem! The fact is I think 300lb person and imagine someone much bigger than what I see in the mirror. Most people guess me at around 250-260.
It's a pain though because if I didn't constantly keep my eyes on the scaled I'd never realise how much I weighed. My aim is to post the next pic at 280 then at 260/40/30 if I get to 220 I may even be temped to remove the shirt