Hi Gil,
A Buc 740? IIRC, that one is close to equal span wings, right? I put 1/2 oz. in our permanent and had no problems. Added a touch during trim flights. I have built *some* weight into almost all my builds (plus the adj. box) and, so far, I have added weight to the box each time.
I don't understand why those would say not to do it.

And remember, I like planes to feel pretty light on the end of the lines, so I fly with the LEAST amount of tip weight I safely can, and fairly tail heavy, all of which lessens the pull.