[texhax] Margins and spaces

[Dorothy Jammins]

Hi all,

I am writing a class for my dissertation and I have a couple of questions:

I am using the geometry package for the margins and I've noticed that the
top margin is with respect to the midline (http://en.wikipedia.org/wiki/Mean_line).
Is this the correct behavior or have I done something wrong?
This is what I have:
\RequirePackage[letterpaper,vmargin=1in,hmargin=1in,bindingoffset=0.5in,
includeheadfoot,nohead,foot=3\baselineskip]{geometry}

The other problem is that chapter headings need to be 1in below the top margin.
I've redefined the \makechapterhead to add a \vspace*{1in} but the space that
is added is more than that, specifically 1 3/16" and goes to 1 1/4" if I use the
setspace package and doublespace the document.

I'd like to make the class file in a way that others can use and avoid hacks and
arbitrary lengths to fit my document. I am using pdflatex and the latest texlive 
(updated with tlmgr) in Debian.

Thanks

d