Don't go runing 50psi on a small tyre such as a pintos. It will more than likely be over the max inflation pressure and an over inflated tyre is just as dangerous as an under inflated one!
I usually run my puntos at around 28 - 32 psi depending on load/ time of year etc.
I run my 195/50/15s at 34 front and 32 rear, I find anything lower and the outer edges wear quicker while the centre of the tread is untouched plus I get better economy as oldhammer pointed out
Mine is a diesel though so heavier engine than a 1.2 petrol