re: Golf Shafts

Try lead tape. Put it along the top of the club along the ‘crown’ line ‘behind’ highest part of the face. You can then add a smaller strip along the top seam of that. Go check Scottie schefflers Srixon driving irons out. Follow a similar placement with lead tape.

I have a Srixon zx5 4 iron and did the same. Helped jump spin up and dropped carry to eliminate some fliers.