I'm trying to run overimputation as a diagnostic on a large data set with 20 multiple imputations from Amelia.  The overimputation diagnostic on one variable takes a long time to complete (more than 2 weeks).  Is there any way to expedite the overimputation procedure?  For example, would using the subset argument to select a subset of cases expedite the procedure?  If so, how would one use the subset argument?  I tried using a vector of TRUEs/FALSEs to indicate whether to keep a row, but I received an error.  Any suggestions for expediting overimpute and/or using the subset argument of overimpute() would be very helpful.