Only guessing but :
The HS has two parallel tubular spars that are offered to two parallel tubes/sockets within the fuselage tail structure. The fwd tubular spar is higher. This would require a very precise, tilting offer, probably by two men holding the HS (with articulating elevator articulating away) and manouvering it in. Unless HS and fuselage tubes were precisely aligned, there would be difficulty mating the pieces. It is not inconceivable that a few tries were required and one or two punctures made into the doped fabric above until a larger leather patch was fitted. The rearmost tubular spar, if misaligned, would bear on a metal stringer. You can imagine 'feeling' it in, missing, swearing, trying again. The man on the elevator side would be getting his fingers jammed between the elevator and HS, if gripping the HS. I can see them punching a hole in the fabric, especially if the aeroplane is being rigged in level flight position, and the job is at nose level !
Another wild guess is that the patch on the Hendon Bulldog is too short, the eyelets should attach to the stringer above.
If you are patching this you should be flying soon, you madman!