mutant neo gene for targeting

[d.m. wright]

I have been trying a gene targeting project in myogenic cells over the
past two years with no success so far.  We chose to use a mutant (weaker)
neo gene because at the inception of the project there were a couple of 
reports that using this gene as the selctable marker had allowed the 
targeting of both alleles with one construct.  I have now heard from 
other people that this is very possibly what prevented our success.  Has 
anuone else tried this or heard of other people that have tried it, and 
what the outcome has been?  Also does anyone know if there is a gene 
targeting newsgroup where this would be better placed?

Thank you,

D.Wright