When trimmed the seq->len was being reduced from the offsets (initial and final). This was the length passed to the elements.
This had two problems:
1) it would not allow you to change the elements not visible (although you likely want to change them as well).
2) the element[0] was always the seq->strips[0].stripdata[0], regardless of the initial trim.
Anyhoo it's all working now.
Thanks Campbell for helping out with this one.
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