Legality? Don't really know, but a lot of pros use lead tape e.t.c. also not to forget Sarazen and the use of lead to create the Sand Wedge.
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just a follow up on the 16 cent backweight. Taping the coins seems to hold up so far. The club seems a little more balanced to me, but perhaps only imaginary. Realizing also there is a little more to "The Secret" than 17 grams of counter weight, the grip itself is heavier and would have a direct effect on swing weight. In any event, it "seems" to help. I have been on the course several times and no problems with tape coming off. Also it is noteworthy to say my grips are Golfpride Tour Wraps and not corded and therefore the feel of the tape is not much different than the grip itself. I do not even notice it is there. I do like the extra inch or so of shaft length. but have not noticed much difference in gained yardage. As for increased control, the jury is still out. But I can say there is no feeling of "less" control. .
Do you have a postal scale or something that you could use to weigh the grip to share the total weight?
According to the Boccieri website, they spec the grips as follows:
The Secret Grip for swing clubs is available in two sizes (Standard and Midsize).
(I read on the Dick's Sporting Goods site that the swing club weight is 92g for the Standard size.)
The Secret Grip for putters is available in three sizes (Classic, Midsize and Jumbo) and three weights (100g, 155g and 165g).
I did not independently verify these weights. I hope this information is useful.