I would suggest to make a loop with the use of memory in which the bit on P1.0 is shifted say 360 times (degrees) and comes out again having the same value but 180 times later. Create a 360 bit shift register. This way it doesn't matter what the value of P1.0 is, P1.1 will always have the same duty cycle.
I couldn't tell you how to do that though because I am not a good programmer.
But here is what I mean.

bit1..............bit180..........bit360
^read from P1.0___^write for P1.1
and start reading the values for P1.1 from bit180