I used to transfer the file over via parallel (PC2Ami) and it wasn't that bad. Leave it for 3 hours or so come back and its done. Hopefully once I get the ethernet setup it'll be sweet.
Dr Dude, your problem:
Not sure why serial is kicking you out half way through.
I've used
chunker from aminet, I'd imagine it's very similar to splitz/Joinz that Paul posted, and transferred the file over via floppy in the very distant past. Lots of disk swaps but it proved that the dechunk/chunk program works and keeps file integrity.
Use it to split the file in 4 and rejoin Amiga side. Chunker does seem slow re-joining on the Amiga side. Not sure if you can add buffers to speed the process up.