Stansted is permitted 50 arr/dept in an hour, even with Winter shedules I count 44 tomorrow between 07:00 & 07:59 so in Summer it should be maxed out.
I'm sure pre-covid someone posted on STN thread that slots were unavailable between 06:00 and 09:00, much to Jet2's annoyance.
In a few years when Ryanair start upscaling with Max10, that is 24% increase in passengers vs 738.
Same with Jet2 738 vs 321.
What STN needs is more Long Haul to reach anything in the 40m pax range but does not have the worry of going cap in hand to increase pax limits.