Change my Archive Style

I have the chateau theme, and that gives two options for how archive posts will be displayed: full post (detail) and concise (just the title and excerpt). Currently I have concise selected, because the other is just too long: http://www.tattedtreasures.com/

What I want is the detail view, but to have all the posts after the first on the index page (and all the posts on search results pages, etc.) to display like the detail view, but to cut off after 15 lines or so. Like on this site: http://www.craftaholicsanonymous.net

How do I make this happen? Any help here is much appreciated.