The Goodman handle allows you to use your fingers with the light in place. If reaching back for the SPG, it's common to slip the light from the left to the right hand, reach back to unclip the SPG with the left, then hold the light against the SPG to "charge the luminous dial", then read it.
There's plenty of other reasoning behind DIR which includes specifics for DPV / scootering. Kind of touches on some of the issues of DIR which is how some people take the best parts of it and incorporate it into their diving whilst others see that configuration as some form of holy writ. Most sit somewhere in between.
There's plenty of other reasoning behind DIR which includes specifics for DPV / scootering. Kind of touches on some of the issues of DIR which is how some people take the best parts of it and incorporate it into their diving whilst others see that configuration as some form of holy writ. Most sit somewhere in between.