I have had exactly the same problem last week. Dickson type holder from RGD which supposedly takes a 10mm tool shank. This would be just OK if the insert was flush with the top of shank – this is rarely the case. I also resolved the problem by skimming 035” from the top of the topslide.
However, I have another post on the forum asking for reports on the Hemingway toolpost kit. Apparently the toolpost block has an overhang which allows the block holding the tool to drop below the top of the topslide. This would allow for a ½” tool – I know this size is probably a bit big for a Super 7, but I have many such tools that I would like to use.
Has anyone completed machining this kit and is it any good as a toolpost?