Claudio,
I'm relatively new to the SL-6000L and therefore not an expert myself, however I'm afraid that your Familiar ipkg will not work. Most of the "ipk" for the SL-5600 and SL-C7/8xx series will work on the SL-6000L, but anything else I believe has to be recompiled to run on the standard Sharp ROM, which at this time I think is the only ROM officially available for the SL-6000L.
As time goes by I guess more ROMs will be available for the SL-6000L, just like there are several already for the clamshell models, the SL-C7/8xx.
Once that happen you could flash your SL-6000L with one of them, just like you did with Familiar on the iPAQ, if you need functionalities not included in the stock ROM.
There is another thread in this news group from another user who has been able to run a "regular" Debian distribution on top of the Sharp ROM, if you are interested.
Good luck with your new Z, it is a little, amazing machine. I have owned if for a month and I couldn't be happier.