I estimate big stack should have gone in with top 75% of hands. Also, if you fold, you get 28% of prize fund if shorty survives and 33% if he doesn't, about equally likely; and 38% of prize pool if you go all in and win. Based on these estimates:

Push with something like A9o, A7s, KQo, KTs, 66.
Otherwise fold.
For metagame reasons, or read-based, it could vary some.