IE7 Homepage GP - cannot fully lock down - hole?

For our site we lock out homepage changes which I can see in internet options
OK.  The kicker is I (or the user) will be able use the home button on the
command bar of IE to add/remove single homepages (including the one that
should NOT be delete-able).  I would like to intro the tabbed browsing to
users and not gp them out.  And I like the home button but despise the drop
down arrow on it (all I need is simple "take me back to the homepage"
function).  I tried tweaking button settings (show/no show) and also
disabling customize buttons so if the button were missing then it could not
be placed back but have not had much success ever with the GP for button
show/no show config.  

Challenge:  How can I keep the home button on the command bar while
following the restriction of -- no changes to the homepage via inet options
ANNNNDD no changes via the homepage button dropdown on the command bar?

Thanks in advance!