Here are what I found for my H10A burns:
4X CLV (TYG01, MCC002) - no rings
8X Z-CLV (TYG02, MXLRG03, MCC02RG20, MCC003, MBIPG101RG04 and CMCMAGE01) - no or very faint ring at start of burn which I presume they correspond to the starting 6X write strategy. The only exception is a TYG02 which experienced a speed drop from 8X to 6X resulting in quite a noticeable ring.
12X Z-CLV (YUDEN000T02, MAXELL002) - the change from 8X to 12X is noticeable. My previous 12X burns with the 4167 DL12 using the same media also showed such ring.
8X and 12X P-CAV (MCC004, PRODISCR05, CMCMAGM01, RICOHJPNR03) - no noticeable rings.
16X P-CAV (TYG03, MCC03RG20, CMCMAGAM3, PRODISCF02, OPTODISCR016, RITEKF1, MCC004, CMCMAGM01, PRODISCR05) - Rings are present in all 16X burned media with the exception of CMCMAGAM3.