Will:
Aren't the 2ndary shafts the same as the primary shafts ? How are THEY sealed? If the leak is that bad, perhaps you could use a seal/grommet from another application. I haven't looked at mine, but I find it difficult to imagine that they are so worn that a serious vacuum leak would result.
You could always richen the mixture a little to compensate for the leak... There is a mixture screw on the Strombergs . I hesitate to start messing with the mixture , however, since my VERY time consuming attempts at this
adjustment with the SU's on my Healey years ago, which ended up almost the same as they started..
David Potter