Thanks Guys for your information, I think I will put a piece if round bar in 3 holes.then set it up true on the lathe bed then drill 2 tapered holes in the top half into the botten half and fit taper pinds to lock it solid, as you suggest it is very unlikley I will ever need to offset the tailstock as as I can do taper turning with the top slide.I can still remove the pins and it will still be in its origonal state.
Thanks to all who responded
John