Well I have a bunch of paper tickets to go through but then I will try the great unreserved Keystone Experiment.
I usually purchase (via 'multi city') PHL-PAO/PAO-PHL/PHL-PAO/PAO-PHL, with one of the return trips being 'peak' for Friday afternoon travel.
In theory there are 4 segments on one barcode which may be used in any order.
So my various experiements in the next few weeks will be:
1- use the two "phl-pao, phl-pao" segments before using the pao-phl segments
2 - use a pao-phl segment first, even if the first segment on the res is phl-pao
3 - ensure that the "peak" pao-phl doesn't get used on a non peak train, on a barcode that has another off-peak pao-phl available.