I'd be concerned about my supply at that time of day, honestly. I know just personally, I'm like a fountain the morning and it can be touch and go at night, which I think is pretty common among nursing women. I'd be worried about limiting the nursing at night, especially if you say you're not pumping all that much off that time of day.
That said, my VERY crunchy ped told me that if I absolutely had to (this was when I was having issues with mastitis and wondering if I needed to wean) supplement or have SO feed dd, as long as they're getting 50% breastmilk a day, they're getting most of the benefits of bf.