I tried the parameters as you suggested for SI 1 as well as SI3, but with no success. But I'm still curious if someone else on the list registered a PDA-like mobilephone (with GPRS support) to his BTS (BS11/nanoBTS1800). If so, I would like to try out his/her SI's settings.
I still don't have the latest version as at the moment our firewall doesn't allow to (I ask the networkadmin later for that).