Test drove the GTB again, was impressed with how it went, although the piston slap is bloody annoying and even when warm it is still there, just very faint... but it doesn't have an aftermarket exhaust to drown it out haha. He's dropped to 4.4k as I bargained him down a bit, so it's pretty tempting
Also, it seems that all the other GTB's on trademe in Chch have also been run on 95, and asked another subaru mechanic and he said that it shouldn't be a problem at all (but reading around on the net suggests otherwise)