Cary,
 My 32 year old daughter had a "sub-total" removal via sub-occiptal last April 16, 2004, leaving about 6mm of a 2.2cm, basically for the same reasons as yours.  The portion remains on the "facial nerve" with no damage to face, eye lid, etc.  She had normal after operation actions in mouth, etc.  Periodically she metallic taste, of course is SSDeafness on tumor side.  Overall she is in excellent condition and spirits are high.  This was done at MassGeneral Hospital (MGH), Boston.
 She had a 6 week MRI to "baseline" the size remaining in order to comfirm Doctor's operation mesurements.  She also had about a 6 month to monitor condition for regrowth, with yearly MRIs to maintain surveillance on the remaining tumor.  Decision to leave some and not cut/graft the facial nerve was both patient/doctor(s) agreement prior to surgery, and to be followed out if tumor displayed problems at time of sugrery.
 Empasis "good" MRI protocol for the surveillance program.  That is patient needs to make sure they are getting the best shots available at the best resolution, etc.  Try to always get copies of your own MRIs for you files/comparisons.  Try to get a Brain Radiologist to always read your MRIs.  Don't let them produce films that are not repersentative of the remaining tumor, make sure they can see it, measure it, and watch it,etc.
        Thanks,  Paul A. Bergeron