Okay, I figured it out on my 478. The 478 has two memory partitions (it seems), ~1.37gb under rgn=77 and ~450mb under rgn=49. I got most of the continental US into 1.3gb, and canada in mexico fit in the rest easily. Sort a pain, but it worked out well. My version of WebUpdater doesn't support the /sacrifice_maps flag, but seems to overwrite maps by default.
I found the information on this german forum: