How to adapt classicthesis layout to B5paper and Linux Libertine

Question

Question says it all: I am using classicthesis with XeTeX to typeset my PhD thesis. I want to use B5 paper size (176 × 250 mm) and the beautiful Linux Libertine font. I'm wondering how to

1. calculate the optimal page margins
2. actually apply these settings to the document

Any help is greatly appreciated =)

EDIT: I should add that I need to generate two different PDF files from this:

1. a version with papersize A4 (210 × 297 mm), where the B5 layout is (approximately) centered, and crop marks are shown, to pass on to the printing company
2. a version with papersize B5 for online distribution, having the same layout as the printed one.

I tried fiddling with using geometry package and \areaset command, but to no avail.

Answer 1

The manual of geometry v5.6 reads:

"The options specified for the area, in which the page dimensions are calculated, are added: layout, layoutsize, layoutwidth, layoutheight and so forth. These options would help to print the specified layout to a different sized paper. For example, with a4paper and layout=a5paper, the geometry package uses 'A5' layout to calculate margins with the paper size still 'A4'."

For your thesis layout=b5paper, of course. Using layouthoffset=((A4 paper width minus B5 paper width)/2) "specifies the horizontal offset from the left edge of the paper", "layoutvoffset specifies the vertical offset from the top edge of the paper": layoutvoffset=((A4 paper height - B5 paper height)/2).

\usepackage[a4paper,layout=b5paper,layouthoffset=17mm,layoutvoffset=23.5mm,%
  showcrop]{geometry}% B5 at A4

respectively

\usepackage[b5paper,layout=b5paper]{geometry}% B5 at B5

should work. And use either geometry or \areaset but not both, because they both try to set the page layout and mixing them can cause unwanted results.