The seven-time MotoGP champion has only one podium to show for his maiden Ducati season so far, despite a string of major changes to the bike including bringing forward the 2012 chassis and switching to a part-aluminium frame at Aragon last weekend.
The latter change was inconclusive, with Rossi feeling the bike had improved slightly, but only able to finish 10th in the race amid tyre issues and following a pitlane start.
Now he is wondering whether his riding position should be next on Ducati's list - suggesting that he is getting less straightline speed out of the bike than predecessor Casey Stoner had.
"We're losing in some quite strange areas," said Rossi.
"For example, compared to Stoner we are a lot slower on the straights, with the same bike as we had from the first test.
"We need to understand this because maybe this riding position is more suitable for the shorter and smaller rider than the taller rider like me or like Nicky [Hayden]. We have to understand if we can improve it."
Rossi said his issues with the riding position were clear to see on television.
"I don't feel very comfortable on the bike, so we've already thought of something to move the weight and if you look at me on the television, I don't ride like in the past," he said. "It's quite clear from outside."
He admitted that Ducati did not seem to be getting closer to resolving its issues so far.
"We worked in a lot of different ways but it looks like we didn't fix a lot," said Rossi.
"We continued to be quite slow. Apart from some good races we are not consistent, and it looks like we haven't fixed the problem."
