Losing pieces of plasmid

[Merideth Kelley]

Does anyone have a suggestion that will keep my E. coli from spitting out 
pieces of plasmid?  I'm trying to put 6kb into a 3kb vector that already 
has 10kb inserted.  Clones isolated after the ligation don't look like 
either the parent or the predicted product.  I know that 19kb is pushing 
it as far as plasmid size, but I'd appreciate any advice.

Thanks

MLK.