I use them at crosses 4 and 5 at the tip of the head. I find they improve my twist second serve and add a more little action that I lost when I went to a poly/gut hybrid. Poly mains.
Extreme Eastern BH, 1x Head IGPMP 12.8 oz, 8.3pts HL with toughgut16l mains and WCSS x's. 1 YTPMP, 1 YTPP, 1 Max 200g, 1 Becker London Tour