I finally cracked a 1:28 at Mallala. The lap i managed it on was the one lap where i had a clean run with no traffic.
On an earlier session that i had a clear run, until the last 2 laps where there were yellows out for a stranded car, i was consistently running 1:29's. In fact, in every session i managed to beat my previous best times

The Eibach Pro-Kit springs definitely made a difference to the handling on the limit.
Having a harness fitted helped me stay in the seat, making the whole experience a lot better.
Getting below a 1:28 will take a lot more practice.....