I have removed all my hose protectors as I found that unless they are super easy to slide down, they just trap salt and sand and corrode the metal fittings. Also they hide hose damage. I have found that in time the hose will usually fail where it meets the 1st stage reg fitting. It starts to become soft and the hose material starts to delaminate between layers. If there is no hose protector you can see this and replace it before it fails. With a hose protector on, the first sign is usually a failure.
With regard to your 40 cu foot I would call it a sling tank, or deco/reserve. A stage tank is one usually dropped off along the way whilst diving, perhaps hung off the down line for use on return. You hit that stage of your dive with the required deco from your stage tank.
In relation to that I was always taught to carry all the gas you require, now I know if a diver does a 200m dive its going to be impossible, but in general, if you drop much of your gas off as stage tanks everywhere for pickup on return, rather than carry all your gas, you run the risk of not finding that stage tanks it for a number of reasons and thus run low or out of gas, in particular when doing deco where you cannot just shoot for the surface when low on gas as it imposes significant risk.