The suggestion that the vang makes up for the main sheet setup is definitely not true. The vang certainly helps, but it's nearly impossible to sheet the boom even close to centerline, and getting it even vaguely sheeted in it completely screws up the shape and twist. A proper traveler would gain you many degrees of upwind pointing performance.
I fully agree with that. My sense is that a traveler over the cabin top would be a complicated project and expensive. And, the boom may not be designed for mid-boom sheeting. I like the solution
@rgranger shows from a sailing standpoint. Liveability is a big problem though. On my Starwind 27, the traveller on the bridgedeck, right in front of the companionway, was a huge inconvenience when anchored or not sailing, and also when sailing with crew (it was great when I single-handed). Sue was always sitting across the bridgedeck and had to move every time I wanted to tweak controls, to her great annoyance! Don't even get me started on the complications of crew position when tacking! That said, I don't know what the bridgedeck looks like on your Hunter, or even if there is one that spans across the middle.
I would consider a traveler a little further back that bridges the seats
and is removable. I've seen examples on youtube and it works well for sailing and is out of the way when not sailing.