Here is today report.
2300 DF: I offered 6oz, he ate 5,5oz
0500: I offered 5oz, he did not finish them.
0840: he ate almost all 6oz offered, without draining his bottle.
So, a partial win.
I have not yet tried to top up before a nap. Next time we got in a bad food/sleep cycle I will try for sure. Now he's sleeping, we are at my parents home, so increased difficulty!