DIANA STEALTH UP DATE

Trying to improve my game and accuracy with my gun. Have a few questions:

I have the Diana .22 AM03 N-TEC, which likes H&N 14.66 and JSB 15.89. I mostly shoot to 25 yards and less. I use for backyard pest control and also shoot at local in door range out to 25 yards. At 15 and 20 yards I can shoot fairly tight groups (for me), but I have some consistency issues (groups open up) beyond 25 yards. That is primarily due to my shooting ability and environment. I shoot off of a deck rail with a towel underneath the gun, and I try and steady the back of the gun with various holds and techniques learning from looking at YouTube videos and the forums. 

What pellets does your Diana like at both 25 and 40 yards? Can you tell me what you have tried and don't like either? Also, can you describe your bench rest environment? i.e, use one rest or two, shooting table, etc...

You mentioned you were getting "One inch at 40 yards off bench." I am trying to identify what you are doing to achieve 1" groups at 40 yards, because I would be content/happy with that too with my Diana.

Thanks