Most Formula 1 teams have waited until the final Barcelona test bolt on and trial their Melbourne configurations.
Di Resta, seventh fastest on the first day, believes Force India will be better served by furthering it's understanding of the VJM06.
"There are things slowly going on, but essentially what we arrived here with is the car we'll be racing at Melbourne," he said.
"We're looking to maximise what we can from that, rather than getting carried away with upgrades.
"Let's understand the package we've got and slowly but surely introduce things that are going to be a benefit in the right way.
"We're fully focused on making it faster."
Di Resta believes the variable weather that has afflicted pre-season Barcelona testing makes it difficult to judge how strong Force India is for 2013.
"I think essentially conditions were worse [on the first day of the final test] than we expected," he added.
"It was forecast to be windy, but it rained most of the day, which we weren't set up for.
"But we've got a bit of an idea if we get hit with some rain for the start of a race.
"I'm not really sure where we are, but if you take where our car was at the end of last year in the rain, hopefully if it rained at a GP we'd be quite strong.
"I think we're further forward at this point than we were last year."
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