Side plank

The challenge is to hold a side plank for 30 seconds on each side, but I was looking for something a little more challenging, and some of the guys on Tribesport suggested this progression (usually you're resting on your elbow with arm and leg down) this engages more core muscles.

Concert today of the Vaughan-Williams, apparently it's live on the radio tonight, for those interested to hear what I've been moaning about...