It would be possible to write whole books on the various problems that people have with valve drills, and the convoluted solutions that some come up with to address their problems.  

Firstly, forget moving the bands on your tanks. Put them at the break of the neck and leave them there. The problem with moving bands is that you cannot simply use sets which are not ‘set up’ for you. Travelling, borrowing tanks from others if yours are in for test or full of gas which is inappropriate for your dive, all are problematic if you rely on band position which is different to the standard – so don’t  be tempted to fiddle!

If you are diving a one piece harness it can be positioned to place the tanks anywhere on your back that you require – there is simply no need to move bands if your harness is set up correctly. 

Position the backplate so that you can just touch the top of it with your fingers when in your drysuit (with no tanks or wing attached). I will write a piece at some stage saying how to set up a harness but in the meantime there are other sources on the internet which will show you how.

The three greatest problems that people incur when struggling with shutdowns are drysuit fit (so many just don’t fit) trim and technique. Trim and technique are at least free to sort out but take time and practice, drysuit fit is quicker but more expensive.

It is natural to lean back when stretching to reach something which is on your back – yet this has the effect of moving you out of trim and letting the tanks slip down your back away from your grasp. Stay flat in the water, or even slightly heads down – as long as you can maintain visual contact with your team.

If you can reach back and touch your valves whilst swimming but not when staying still to do a drill, you should consider that it is perhaps your trim when stationary which is working against you. (It is easier to be horizontal whilst moving)

Hunching your shoulders over to bring the valves closer is another natural act – but stop and think about it. Those tanks are attached to a metal plate which is not going to bend with your back! Keep your head up and back arched to hold trim and the tanks stable and within reach on your back.

Your shoulder moves more efficiently if you work with the joint rather than against it. Rotate your shoulder in the same way as if you were combing your hair rather than saluting – your elbow should be close in to the side of your face rather than sticking out the side. Most people gain up to an inch of movement like this – which can be enough to reach that valve.

Get feedback. It is common to feel that you are miles away form the valves when you are within a hair’s breadth of reaching. Get friends to tell you how you are doing, remind you to stay flat and arch your back. Video/photographs are good too.

Stretching out at the start of a dive means that you can get any excess material in your suit and undersuit up to the torso where if will assist you in moving. If you are diving dry make sure that you equalise your suit regularly to maintain this degree of movement. It does not need a lot of gas to do this, ambient pressure or just below is fine, just regular adjustments.

Stretching between dives helps too if your shoulders are not that mobile. I was unable to reach my left post when I first tried to dive a twinset and stretching exercises helped enormously. Cameron has written some excellent articles on this at www.divefitness.com  

Practice, patience and perseverance are crucial in gaining this skill if you struggle. A sense of humour helps too – don’t give up!