I can't figure why George O. ever setup a "family" boat this way.
On the original DS1 there was a fixed jib block mounted on the side deck, with a hole to lead the sheet through the wooden coamings. That avoided any "hard spots" in the back rest.
Later, the block got changed to a small track, for better adjustability, and the tracks were mounted on the inside of the coaming, as you can't mount anything on the top of a wooden coaming...
From a sheeting angle, the side deck, or the coaming, are too wide for closehauled in say 8-12 kts. People who care about that mount barber inhauls on the cuddy top to bring the jib sheets in a bit more under those conditions. I added them because I had an old jib that wouldn't set properly once the wind got above 8-9kts unless I used inhauls - it would flutter instead. The effect was dramatic.
Before we get completely off-topic, this looks like an impressive rig. Does it hook over the transom? Does it also hook into the rudder gudgeons?