They are an excellent aid to recovery. However some cautions when fitting them.
1) they need to be as far back as possible. Because the bow is narrow and by the time the shoulder nestles between the poles, the keel has allready run the wrong side of the first set of rollers
2) remember the width of the whole rig will be about another 4" and any side scrape will cause substantial damage to the unlucky bugger in the way!!
3) As the poles are protruding then they need to be marked with reflectors like LimeyDal's.
In my experience the flat boards around the rollers are more effective than poles. Dissadvantage is that the hull is obscured when on the trailler. But hey ho.