You can go ahead and start feeding both a small rat every 7 days if you want.
I always bump up feeding schedules from 4-5 days to 7 days once a snake hits 500 grams. Both of your snakes sound more than ready.
Thanks! And aside from difficulty of doing so, is there any real difference between me feeding it one large prey item (of appropriate size, of course) versus several smaller?
I ask because I'm going to have a LOT of leftover frozen smaller guys.