Has anyone ever noticed that the SR chart never made any distinction between Specialist Mages and normal Mages, even though Specialist Mages have more spells available to them? Or that the Wisdom related bonus spells did not affect the SR at all for Clerics? In my campaign, I had a character who was a Cleric Mage, and I could not decide how to rate their SR, so I converted the number of spells into the number of spell levels. Then I related it to the Major and Minor helms by spell levels, this also allowed a person who had cast a spell or two to figure their SR according to the current number of spells memorized. (I do not arbitrarily rule their SR goes down if they cast a spell, it is entirely by spell levels memorized when they power up a helm.)

Lea's SR Chart
Major  Minor  Spell Levels
 Helm   Helm     Memorized
    1      1         1 - 6
    2      1        7 - 13
    3      2       14 - 25
    4      2       26 - 31
    4      3       32 - 38
    5      3       39 - 64
    6      4       65 - 84
    7      4       85 - 93
    7      5      94 - 110
    8      5     111 - 138
    9      6     139 - 161
   10      6          162+

I also ruled that if a magical item had stored spells such as ring of spell storing, that they could not access those spells if they were sitting on the helm, but they could use them if they had been sitting on the helm and were 'blanked' from contact with the helm.