Perhaps you guys could use an impact bag - I do it against the side of my bed(something I should do more of too). Keep hitting it in a continous motion back and through.
Whilst your hitting the bag you can concentrate on these things...
Do you feel the pressure against pp4?
Did I maintain a stationary head?
Do I feel extensor action on both backstroke and downstroke?
Did I trace a straight plane line with my pp3?
etc
You can become very productive with these things.
