question for the machinists in the house

It looks good. I think that you could easily get away with 1/2" heims instead of 5/8" parts tho. If you think about it, the heims work in pairs because there are 4 of them. I would use a 5/8" on a pannard bar, but 1/2" is probably overkill on a watts-link. The radial load rating on a good set of 1/2" heims is obscene!

A JMX8 1/2" has a radial load rating of 16,242 lbs.

A JMX10 5/8" has a radial load rating of 17,959 lbs.

The numbers suggest that you could get away with 3/8" heims on a watts-link with no sacrifice of strength over a pannard bar with 5/8" heims.