algorithm limits

General question: What are practical limits on the magnitude of OMEGA that is compatible with the FO and FOCE/I method? I seem to recall Stuart at one time suggesting that a CV of 0.5 (exponential OMEGA of 0.5) was about the limit at which the Taylor expansion can be considered a reasonable approximation of the real distribution. What about FOCE-I? I'm asking because I have a model that has an OMEGA of 13, exponential (and sometime 100) FOCE-I, and it seems to be very poorly behaved in spite of overall, reasoable looking data (i.e., the structural model traces a line that looks like the data, but some people are WAY above the line and some are WAY below, and some rise MUCH faster, and some rise MUCH later, by way I mean >10,000 fold, but residual error looks not too bad). Looking at the raw data, I believe that the the variability is at least this large. Can I beleive that NONMEM FOCE (FO?) will behave reasonably? thanks Mark <<attachment: left.letterhead>>