If the list of recently opened files is too short here is a solution that worked for me:(taken from OO authors page)

t his is a quote from the OO Authors page: "You need to edit one of the configuration files. Before you do that, close all OOo windows, and also make sure that the quickstarter is closed,too." search for this file: ...\user\registry\data\org\openoffice\Office\Common.xcu
be sure to use only the file that is in the above specified path. On my system there were many files like this:

/home/dave/.openoffice/user/registry/data/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/data/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/en-US/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/af/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/ar/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/ca/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/cs/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/cy/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/da/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/de/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/el/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/es/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/et/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/fi/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/fr/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/he/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/hi-IN/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/hu/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/it/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/ja/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/ko/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/nb/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/nl/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/nn/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/ns/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/pl/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/pt/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/pt-BR/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/ru/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/sk/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/sl/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/sv/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/tr/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/zh-CN/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/zh-TW/org/openoffice/Office/Common.xcu
/usr/lib/ooo-1.1/share/registry/res/zu/org/openoffice/Office/Common.xcu

the first one is the one to use - be sure to use your home directory name
not mine - this is just an example:

/home/dave/.openoffice/user/registry/data/org/openoffice/Office/Common.xcu

In this file find the line:

<node oor:name="History">

directly after this line add:

<prop oor:name="PickListSize" oor:type="xs:int">
<value>10</value>
</prop>

this will make the recently opened files list contain 10 files.