Maybe yes, maybe no. Sump isn't really about adding water volume to the system, it's primarily there to enable effective surface skimming of the main display and secondarily as a place to put unsightly equipment. Depending on the ratio of display to sump, lower baffles will provide greater overflow capacity in the sump versus higher ones. In the case of the OP, display to sump ratio is about 2.8, which is good, and he certainly could raise the baffle height if desired, however, not really sure what the benefit would be (beyond the requirement to have 7" depth for the skimmer).
Not maybe, it's a mathematical certainty that it adds volume to the overall system and the more volume the better as proof from how difficult Nano tanks are to maintain consistent parameters compared to larger tanks or the fact that dosing errors or pollution won't have a greater effect on a large tank compared to a small tank.
In my opinion, utilizing the maximum amount of water without overflowing the sump when turning off the return pump is advantageous.
I'll use my 29 gallon sump for example. If I set my baffles to 6" I would effectively cut my sumps volume in half from 24 gallons to 12 gallons. While the loss of 12 gallons may not sound like much it's essentially 15% of my total volume. (90 gallon display with an estimated 30% displacement from rock, sand, livestock, equipment)
Furthermore, depending on the setup, if I had a 6" baffle height the flow through the sump would be so rapid the baffles would likely not allow sufficient time to pop and therefore would get sucked into my return pump and into the display. So many people put a valve on their return pump to slow down the flow. This is counter productive. A) you wasted money on a bigger pump your're not utilizing and B) For most systems, we can never have enough flow.
And finally, I'll reiterate my second point from my original post, had the op setup the baffles to a greater height initially, any future replacement of a skimmer that required a different water level would only require that a new stand be made, which is cheap and easily accomplished.
It is for that very reason we are having this discussion.
Your point of hiding equipment is valid and rudimentary. Surface skimming is a good point too as an overflow clears the top layer of water allowing for better light penetration and increased gas exchange and oxygenation. However, your points don't contradict mine. They are simply other benefits of a sump and not specifically water level/baffle height.
Here's a good read by Marc Levenson from Reefkeeping Magazine that reiterates some of my points.
