Tom,
I have done a restoration of a 1974 AMT 1/650 Enterprise and I can tell you about my solution; if you don't mind.
I went to a beauty supply store and picked-up some fake finger-nail polymer (powder) and nail liquid (monomer). I had some plaster of paris I
could use and most of the other items I used I had on hand.
1. This is the plan. I would use the spare Round2 pylon to make an impression of the male tab portion. I used a carpenter nail bulk packages, actually 2 of them, to hold the plaster while I made the impression. Cardboard would absorb the water from the plaster too quickly and make the stone set too quickly. That's the reason for the plastic packaging.

2. I filled the packaging with a bulk of stone and then, after painted stone onto the pylon itself to capture the detail, I gently laid the painted pylon into the wet stone supporting it with the storage lids. Here I also had to make sure there were no undercuts in the stone or in the pylon so the second stone half would separate from the first.

3. I applied liberal amounts of separator, Vaseline, to the first half so the second half wouldn't bond with the first. I also used Vaseline to fill any holes in the first half as well as blockout some minor undercuts I had. I took the second bulk nail packaging and cut the bottom out to allow me access to pour the second half. I made another mix of stone and, after painting the exposed pylon with wet stone, taped the second package to the first and quickly filled the second half with the stone.

While the stone was setting, I prepped the restroation pylon to allow for a finish line and to allow more surface for the fingernail acrylic to grab.
4. Then, I separated the two halves and took out the spare Round2 pylon. This left me to halves of the impression. I applied liberal amounts of Vaseline to the second half and blocked out undercuts.

The second pylon needed some additional reinforcement as it didn't have enough surface area for the new acrylic to grab on to. I had some old dremel burs I had broken the head off during use, and superglued them to the inside of the restoration pylon.

I mixed up an approximate 2:1 polymer to monomer acrylic until I got the consistency of warm butter. Working quickly, as the acrylic set time was around 5 minutes, I painted the restoration pylon with wet acrylic and then set it in the first half. Placing the remaining wet acrylic, which was now like play-do consistency, I carefully placed the second half over the first and gently closed the two together. I placed a 4" C-clamp around the mold to help combat expansion. (Didn't know if there would be any, but didn't want to take a chance.)

5. After about 35 minutes and constantly checking a small sample of the same batch of acrylic for hardness, I opened the mold and, after cleaning off the gross flash, here is the restored pylon support tab.
6. Once I had glued the second pylon back together, I used the same process to create the support tab on the second pylon. Here are the two pylons together. I still needed to do some finishing and sanding before they are ready to assemble, but at least I have something to work with now.

For the secondary hull, I had to break it apart as well. I couldn't think of a way to salvage the original nacelle supports, so I ground them away with a Dremel bur.
I scratch-built some recepticals for the tabs and surrounded them with Millput to make sure they wouldn't break again.

Then I built the pylons per my usual tactics. It is a lot of work but as you can see in the
gallery link it looks pretty good.
Apologies for the long post, but I thought you might be interested in the process I used to make the tabs.
Hope you enjoyed reading!
Let me know if you have any questions.
Steve