On the ones I had, there was a plug on the bottom of the carb, allowing one of the tools to be screwed in to push the jet up to lean off the mixture.
If the jet had to be pushed down to richen the mixture, the other tool was screwed into the damper hole at the top of the carb (after removing the damper), and the slotted spacer(3rd tool) put into the carby inlet so that the jet could be forced down. A fiddly business, and I suspect Stromberg had several methods to deal with mixture adjustment after emission controls came in.
Top adjust needles, as you describe, seems more sensible than the ones I had.
Cheers,
Lionel

