While I don't intend to sound as if bashing is at hand...I agree that Dan's architectural engineering tends to go a wee bit too far sometimes...while when I viewed other plans of his...things looked better than my impression of the OV-10.
There are a few specific concerns...the two piece (front to rear) sectioning of the tail booms with nylon bolts. While anyone who has ever seen an OV-10 fly would know they yaw an awfully lot when they reach ground effect... it is going to catch most pilots by surprise at the last moment...unless they land it hot. With this yaw is going to come a pretty severe side load as the plane initially touches down and more or less yanks in the direction of the wheel initially touching. The resulting pull in the opposite direction creates a whipping action for the booms, horiz stab and all joints past the wing.
1. Making the boom a single piece and gusseting the joints between the formers and attachment points with small balsa triangles will serve to strengthen it back there.
2. Converting the wing into a three piece by clipping outside the nacelles will prove to unitize everything.
3. The same yawing motion described earlier will work against the nose retract mounting location as well. The nose will get caught in the middle of that initial mains whipping action. To counter this you can create an elongated "z" doubler which will run from where it serves to strengthen the nose retract mounting...then runs back along the cockpit sides, then up just behind the observer/weapons officer's rear seat to a rib shaped piece in the wing's center section locked to the spar(s). This need be no more than lite ply laminated to the balsa along sides of the cockpit from the retract mount in front to becoming a doubler in the wing. Having built a prototype for my 1/6th OV-10D NOS-NOGs it became obvious this doubler would serve Dan's design even more because of its light weight design. At 1/6th the all up is targeted at 26# with a pair of Saito 120DP's.
4. As for people who've built Dan's. Gregg Hahn flew one in team scale built by someone in Ohio back about five years ago. I believe it had MDS 108's and was an absolute rocket...far from prototypical speed and maneuvers that took a ton of sky instead of the tight pattern the OV-10 was designed to provide. The fastest the full scale is capable of flying outside of a dive was 287 mph and that was the D+ with Garretts.