If you want to go heavier and stay on the safe side, the looser diamatered JSB Exact Heavy's (10.2's) fit great in my 350 clone and may be the ticket for your Diana. So if the Kodiaks, RWS SM's, and H&N's fit tight, try the JSB's. They give mine a nice healthy 'pop', and slap what they hit pretty dang hard!!!!Accuracy,....on par with the rest of the JSB line of pellets!! tjk