When reporting Outlays and expenses on designation of a property as principal residence, if there are two owners do you split the outlays and expenses 50%?

It depends on the exact question being asked to you.

If the questions is "Total outlays and expenses related to the disposition", then you don't need split the numbers. You enter the total value and based on percentage value entered on the screen "Sale of your Principal Residence", the proper percentage value will be calculated. 

If the question is "Outlays and expenses related to the disposition", then you have to calculate your portion of outlay and expenses (e.g. 50% of total value).

You can also verify on the T2091/TP274 form when you print your return to check if value you want to claim is entered on the Outlays and expenses line.