You might be able to do what you need to do like this:
Method A - manual account db update
1) create the printer however you can (named impnf, for example). Be sure not to use any spaces in any of the available fields or the 'db accounts set imp_nf...' command shown below will do odd things...
2) note the output of db accounts show impnf
3) create the printer you want using db accounts set imp_nf `db accounts get impnf | sed s/\|/\ /g`
signal-event printer-create imp_nf
Method B - using a custom template fragment
1) Create the printer however you can (named impnf, for example)
2) open /etc/samba/smb.conf and locate the configuration directives related to 'impnf'
3) create a custom template fragment in /etc/e-smith/templates-custom/etc/smb.conf named "50customprinter", containing the same data collected in step 2, but with the printer name set to "imp_nf"
4) execute signal-event workgroup-update (this event updates /etc/samba/smb.conf and restarts smbd).