I think this is an improvement on the original concept in that it provides for the first time a way of mounting the board which looks mechanically credible, ie could actually be removeable, firm while in place – and with a limited ability to fold back in the event of striking something. As you say, “half way” between a dagger board and a swinging board. (I guess it is held in the vertical position by a “weak link” (breakable dowel peg))?
A dagger board right at the bow, which is what this essentially is, might perhaps need to be able to break out of the slot in the manner you have drawn. I take it there is some sacrificial component pinning it in place? (Maybe a bungy would be better than carrying a bag full of replacement dowels). Otherwise the bow transom would need to be good and strong to absorb the impact of the leveraged board hitting the bottom, the dinghy and contents having potentially quite a lot of momentum. I still don't like it much. As David points out, it is an inherently directionally unstable configuration - you won't have time to tie your shoelaces with this one, in fact I'd be inclined to leave my shoes ashore.
We have to ask why a tender should be sailed at all. In my experience it is mainly for fun, will take place mainly in the sheltered waters of an anchorage, often involving children, and where I live, almost certainly off a gently shelving beach. A dagger board on such a tiny dinghy perhaps makes more sense than a swinging board – both have their merits - but there is no way I would put it in the bow even if it proved possible to sail with it in that position. I leave that to you, in your beautiful sailing grounds.
Arne wrote: “…and the board itself could be fitted and removed from the safety of the fore thwart”.
I think I would remove the word “safety”, as an adult kneeling on the forward thwart of a lightly constructed 8’ pram dinghy is going to have an interesting effect on the trim if there are no other occupants. If caught in a squall and a bit of a chop, at the head of a bay, you’d want to be careful doing that. Don't forget the clutter of the mast and sail right up there as well, and all that needs to be negotiated while retrieving the board and bringing it into the dinghy, in the event of needing to revert to rowing.
I return to my original question “why?” and have now convinced myself that if the dinghy were mine I would simply give it a little bit of fixed draft, by way of a deadwood keel from the forefoot to amidships. Then a pair of matching (depth) skegs aft, as I agree this is best if you are dragging the dinghy down a concrete boat ramp.
(If it were lightly and nicely built, like Annie’s FanTan, I think I would rather carry it on my back like a turtle, which is easy and often done here.)
With the amount of rocker you have, an increase of 50mm in the draft full length would probably be enough to sail to windward, and it would sit nice and flat on a trailer or upright on a roof rack too. And maybe it would row better too? (I am not sure.)
Anyway - I am sure I am not alone in awaiting with considerable interest (and a certain amount of anticipation) the results of your trials with the bow board. Your willingness to push the boundaries is admirable. I am sure the Wright Brothers were given as much skepticism from the sideline.