installing SGI SVR3 from tape

Howdy; I've got an IRIS 3130 I recently rescued, along with a shocking pile of tapes. Among these are what appears to be complete OS install tapes for GL2-3.6 (SGI's UNIX didn't come to be called until the first 4D-series machines were released) and 3.5r1. For various reasons I am interested in performing a new system installation. Booting from tape is (obviously) in order, and a tape identifying itself as the "boot system" is present. If I 'boot sq0' the QIC spins briefly and complains that it can't find the default boot file. Supposedly there is a stand-alone utility called 'sifex' which can be booted from tape to initialize disks and the like, but if that's on this tape it's not letting on. 'boot sq0:sifex' returns with an error to the effect that 'sifex' can't be found on the tape. I'm missing something but I don't know what. Am I trying to boot the wrong tape, or is something else going on? I suppose it would be worth trying to read a few of the QIC tapes while the system is up, but if someone knows in the meanwhile what my problem is likely to be, it'd be helpful. ok r.