The only thing I can think to do is write a plugin that changes the posts display for certain threadids.
Hmm, it would have to be for various new threads. Some are just regular posts, which I'd still like to have 10 per page. Other contain copy/pasted info and attachments with thumbnails. These just *really* slow down load time as the pages are HUGE if they have 10 posts like that.
I posted another request for end the page based on # of attachments being displayed on the page. THat would work too (might be easier?) Count # of attachments in the posts on that page and end the page as soon as it hits say, 100. ( ??)