To be honest I've sidestepped the issue now that GPT4 context size has increased to ~8000 tokens. None of my content goes over that limit.

I did build in a "chunking" mechanism to break down the article into sections if it was over the limit, but I'm not entirely sure how effective the summarisation would be for those... Summarising the first part of an article and then doing a separate summary for the n-th part would probably make confusing results when recombined.

Might be some "prompt magic" that can make it possible, but for the 90%-case I bet you'd get perfectly useable results just by using the first under-limit part of the content. Not tested that idea in the real world yet, though.