Bottom line is balance and inertia.
You want the stabs to help hold the bow (balance) and you want them to help keep the bow in place while the arrow is coming off the bow (inertia).
The most efficient way to achieve both is to have an extremely light and rigid bar, with weights at furthest point....moving it moment of inertia furthest away, requiring less weight.
some newer hunting stabs sacrifice the balance (lets face it, a <12" hunting stab isnot going to balance out these parallel limb bows) and puts a big honkin weight on the end. This more than satisfies the inertia requirement and is why guys see a noticable improvement, but then get form and fatigue issues when shooting a lot of shots. Your body needs to be in the right position to shoot these well.
I agree, the 4"/4oz ain't doing squat other than adding 4oz. Much better to hang it off the back and get some length out front.