Hi Andy,
not a bad shot for your first attempt, but with the lens you have you will only get 1:2 magnification which is half life size you need to get a true macro lens for 1:1 life size reproduction, two good lenses are tamron sp90 or sigma 105 both cheap and excellent iq.
another road to go down is smaller prime lens and tubes or a dcr150 or 250 but as never used the dcr adapters can only advise to look at some shots on here taken with them and decide for yourself.
hope this helps alittle
Gaz