When to move up in drills

Been just starting to do some dedicated drilling sessions with a practice partner, but we're still at the point where our placement is a bit sloppy and the ball falls out of play fairly often. Would it be worthwhile to add in some mixed drills (e.g. like the X drill where one player hits down the line and the other hits diagonally), or should we focus on the basics until we're both fairly accurate?

Hi Mark,

I would stay with the set drills for a little while till you get more comfortable placing the ball accurately.  Then you an move on to the Xs and Hs drill or more random drills.