You should have a quantitative idea of how much additional power this bolt gets rid of, by doing some testing. I guess the 1/2 inch long one adds a quarter watt of capability and the 1 inch one adds a little more than a half watt, at maximum allowable temperature. Not much help for that much ugly. And not better than the watt or so capability of small clip on heat sinks.
A TO-220 on no heat sink, at right angles to the board gets rid of about 2 watts if it is 100C above ambient, but something like 40 watts if it is mounted om a huge heat sink. So, I think your bolt idea is incrementally helpful.
My favorite trick, like this, for axial lead diodes, is to solder a small loop in the lead, before soldering it into a board, giving it Mickey Mouse ears. Also incremental, but there is no real good alternative for heat sinking axial leaded parts, except for soldering them between copper planes.
I use threaded spacers as heatsinks fairly often. It is the same idea but lighter for how much heat it can carry way. If you put the screw in from below the PCB, it will works as the holding nut and the heatsink too.
Somewhere I saw a board that had long slots routed for the diodes (generous air space on each side of the cylinder), with the rather long leads soldered onto large copper pours (maybe a square inch, each).
I guess you can get something like 6 amps average from a large axial silicon diode that way, without mounting a heat sink. Cheap, but it eats board area.