for the Beta with the 320 donk plan on 32 liters and you SHOULD be pleasantly surprised, as long as you only pull max continuous as per the book.
With mine I can peg it at 28.2 all day every day during mustering during the cooler times.
With the Beta 11 and the 360 donk be prepared for any surprise even if you plan at 38 liters. It depends on the carby fit, how you hold your mouth, the prevailing temperament of your chick, even if the sun is shining, things can go haywire.
28.2 is really good for the clients, who pay for the fuel, and, don't pull over the red line, it plays havoc with endurance, the bosses temperament, and other things.
Just a little tip with different temps and normally aspirated donks.
The old '47G5 used to have a total endurance (to MT) of four hours fifteen on a 22 to 25 Degrees C very dry day with winds running at 18 to 25 knots. (spare energy of the bonus type)
On the hot days of 38 to 40 degrees C no wind and a bit of humidity around it was three hours ten and silence.
In other words the endurance used to vary by well more than the old times legal reserve requirements. Nowadays the rules stipulate that the operator must set their own standards, no need to wonder why they changed the rules.