Melandri has yet to break into the top 10 in a qualifying session or a race this season, while his teammate Casey Stoner won the opening round in Qatar and lies fourth in the championship.
Preziosi says the GP8 suits Stoner better and aims to make technical changes to help Melandri get more out of it
"Marco can't feel at east with the bike and he's suffering a lot because the results we expected are very far off," Preziosi told Italian magazine Motosprint. "Our bike has characteristics that suit Casey and to have him as a teammate is very tough.
"It's very aggressive in both the frame and the engine and Casey likes this because it allows him to feel the bike more. But Marco is disturbed by it because he needs a less aggressive bike.
"To help him we must make his bike less rigid in the chassis and less aggressive in power output. We need to improve the rideability."
Preziosi believes that the Honda is currently the best bike in the field, but has also been impressed by rookie Jorge Lorenzo's start to the season.
"I think the best bike is the one leading the championship," he said. "Honda and Michelin have always been my technical reference points, just like Rossi is in the rider's department.
"I'm not surprised Honda and Michelin are ahead because Pedrosa has had two good races. Lorenzo's performances have really impressed me as well. Even Pedrosa and Stoner didn't go as fast on their debuts."
autosport.com