I'm reading "no cry sleep solutions" at the moment, and one suggestion for getting longer naps is to wait for baby to get to the waking up point ( in your case about an hour after last feed) and BEFORE bubs is fully awake, resettle baby via rocking or whatever else works that isn't feeding. she says it takes about a week before bubs is used to longer sleeps. this advice was for naps during the day but might work at night too

at least its something different to try.