keeping inline images inline

I'm working on a document filled with math, but have been trying to
get around using MathML since learning DocBook XML alone is more than
enough of a challenge for me.

In particular, I'm trying to get an inline image of an equation to
center vertically according to the center a printed line. However, it
really wants to center vertically based on the baseline.  So, with a
simple equation like D/Dt the / (which is really horizontal in the
image) lines up directly with the baseline, with D inline with the
rest of the print and Dt hanging below the line.

For example,

<para>... the velocity components, respectively. 
                        <inlinemediaobject>
                            <imageobject>
                                <imagedata fileref="graphics/eq1.eps"
format="EPS"/>
                            </imageobject>
                        </inlinemediaobject> 
                        is the material or total derivative. 
</para>

looks something like (if your mail client spaces this like mine)

the velocity components, respectively. D is the material or total derivative.
                                                                     Dt

Is there a way to make the equation center differently so that the --
(divisor?) lines up with the middle of the text line? I'm using
oxygen, xml and a Mac. Since I haven't found an affordable
alternative, I'm using FOP.

Thanks,

Cassie