Apart from being a short stack or a huge stack, should we ever be happy to flip?

I must admit, I never know what to do and even when I call and win, I don't know if I made the right play. Today I was faced with a flip in each game - each the reverse of the other - and so I feel it's pertinent to ask now.

In both games I was going strong - 150 of 550 runners and 45 of 1700 - with 2.5x and 4x the average stack respectively, I correctly assumed both shoves were light and that I'd be flipping at worst.

First I raised from MP with 88 - villain shoved with AJ - and in the other game, villain open-shoved from HJ with 55 and I called from BB with AJ. I lost both races, half my stacks, and left looking over my shoulder.

I was a bit reluctant to call with AJ call - and would be crushed by AQ/AK - but my instincts were on the ball and I guessed I'd be no worse than 45/55 so is it ever correct to race when you're in a good position but you stand to lose 30%+ of your stack? On one hand I would say no but on the other hand, you've got to take chances in tournaments.

I think you need to be thinking about your equity against V's range and we should be taking spots where we think we are +EV ( ideally 55%+ equity) - so generally spots where there are more hands that we dominate than dominate us are ok - so you don't give stack sizes but both these are probably OK unless we think V is very tight. Have a play with a programme like Equilab - that might help you to be more confident you are making good decisions.

Thanks. Though I was right in guessing villain had over cards to my 88, and you confirmed I was right to call, it still makes me wonder if I should have folded and choose a better spot than a con flip, especially as I was well-stacked at the time - but maybe you have to take those chances to succeed in poker.

It really depends on the odds and equity, like oldgoat said. At first glance these spots sound like std get ins, but without knowing stats/stack depths/etc it's hard to say. It'll help if you do some study off the table to see what people should be going with and what hands you should be defending. If it's <~20bbs you can look at some charts people have made for starting points (Turbokings, DTOpoker, ProPokerCoaching, MaxValueShovenCall, etc.)