For maximum protection you really want to wait until the oil is upto temp. This isn't the same as Water being up to temp which is what the standard gauge shows. Does the ST have an Oil Temp gauge as well?
Oil normally takes about 15mins to get up, whereas water takes about 5. I wouldn't worry though, sounds like you did it when the time was right, and you still didn't take it upto the limiter at over 7k or anything!
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Stripped Saxo VTS - 135bhp/tonne!