I'm even tighter when I have the lead but I will bully if I'm in a hand and think I might be losing. That said, it doesn't happen too often. I don't like being in the lead, I prefer to be top 25%. I find that I can still play my game and steal a few blinds when I'm positioned in the top quarter of players that are left.
When I'm short stacked, I will generally wait for a pair to go all in and either steal the blinds, double up or get knocked out. I won't do it when UTG though, it's just too dangerous.
I'm a tight player either way but tighter when the big stack. Yes - I think that size matters.