I'm afraid I spent too many years either at a drawing board or the manufacturing end of precision drawings to enjoy using either a computer design package or following the constraints of a rigidly dimensioned design.
That's not to say I do not accept the challenge from time to time to meet tight dimensional boundaries but as an everyday way of passing my hobby time I prefer to, as Tam says, do a rough pencil sketch that most likely fits the piece of wood being considered if it is not immediately obvious, and feel free to deviate as the project unfolds rather than fight the medium to meet a dimensional target.
It's a bit like the whole concept of being retired I suppose, 99% of the enjoyment is not being restricted by time and other boundaries other than those of common decency to other people.
I always feel that having generated a turning design on the computer it is just waiting to be fed into a CNC machine to produce it.
