Most tailstocks use that method of fastening, it's just that the 7x lathes do it rather crudely.
If you have a mill or get a milling attachment for the lathe you could easily machine one out of a small aluminum or brass block to fit beneath and between the ways more precisely.
While you are at it you'll find it much more convenient to convert to a lever and cam to lock the tailstock in position, rather than having to use a wrench each time; it's probably one of the most common mods for a 7x and you can either buy a kit from the LMS or there are numerous plans freely available online.
M