Hmmm interesting. Bet a little optimization could have reduced several hundred megs, or more. Bit of a pain every post is over a gig.
edit: A lot of PDF's that could have optimization or be unoptimized and let lzma do a better job; jpegs that could be optimized and then leaving uncompressed in the epub's so when packed together you save the size of the image (since it's a copy of the cover image, possibly twice if the covers are stored with stories so duplicates can be optimized out). A number of pdf's that are scanned books that with a little cleanup can be reduced to 1/3rd their size, to basically no quality loss, though they'd be better to be OCR'd. Some covers can be removed as they are just previews of the first PDF page without a cover image, etc.
Seems like a lot of work to do.