Attention NOOBS!! It is natural for it to slide left, and it very well may slide left if you give full right trim, the trim only makes small adjustments, may not be enought to compensate for the left shift caused by tail rotor. I just checked my heli, on full right trim, it doesen't slide either left or right, when it's about to get airborne-it then pitches to right, just a few clicks from full right trim-it does indeed slide left before pitching right. Every heli is different-so yours may have slight bias to the left, but no way to know until your hovering. Also when your hovering, you will notice a right tilt-that is also normal.