From my portfolio...

I have over 3000 notes so these stats should be pretty good. Days 1,2,3 clearly win.

So when a Thursday falls on the 6th of the month, then that Thursday's payment will include payments due on all 3 big days (1st, 2nd, 3rd) of the month. This produces a payment of about 15% of the month total, vs the normal daily payment which averages around 3.2% of the month total. On the average, each Thursdays should pay about 9.7% of a months total.

Great detective work BruiserB.