Pete, I'll try my best
Anyone with a photo please send it. Pictures can really clarify things. Like the prop balancing thread. I thought they were balancing props.
The picture revealed they were balancing prop engine combination.
My drawings are older and I have no tabs shown on the drawing, just bushings, and tubes. Here goes.
horizontal- page 19 shows two 4" long tubes with 3/8 bushings welded perpendicular in the center on the side of the tubes. One is 7/8, one is 3/4.
The long tubes act as sockets for the horizontal tubing coming in from both sides. the bushing is the fuselage attachment.
pg 25 will show two 3/8 bushings welded vertically through the top longeron tube. a bolt goes through each and through the bushing on the 4" tubes.
You may consider staying a little long on the bushings. Can quickly be filed, ground or cut down changing the incidence and relying on something other than a stack of washers'.
Vertical- page 25 has a 7/8 top of the tail post to act as one socket and a 5/8 tube welded to the top of the longeron for the front socket.
hope that helps
Tom XL-7