You posted recently asking about Regs on your HFT500.
People replied saying that it would probably have a good sweet spot with a low spread in fps over that sweet spot. Did you understand what they meant re sweet spot?
10.8fp is @ 760fps.
What pressure are you filling the rifle to?
After how many shots are you measuring 10.8fp?
10.8fp is fine if the grouping is good with those pellets at that speed as said above. Most will run the guns at @ 770-780fps which will be up to @ 0.5fp higher than yours. You wouldn't really see any great difference between 780 and 760fps up to 45 yards.