I have just made a version of Harold Hall's QCTP for my mini lathe with a couple of modifications.
I used two locating keys and a lock nut for the height adjustment instead of a grub screw.
One problem I found, was that. because of the extra overhang, there was more judder unless the top slide was wound fully in, this may apply to all QCTPs.
The other problem was parting off, the tool jambed and broke the operating piece, I have now remade this using 12.5mm steel and it is much stronger.
Apart from this it seems a useful bit of kit.
Regards Clive