Im told wheel collets for planks do the job well. Also I think align supply them as part of the kit for the 450's now so they should be available as spares. These should fit your blade. They work because they increase the mass and inertia of the flybar and therefore the ammount of effort needed to move it. This in turn affects the helis flying.
As far as the expo goes... Theres no harm in trying it. If you dont like it, roll it back off again.
Good luck with it
... Azzy
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JP Bell 47 Twister
Align T-Rex 450 XL (well it was once)
Align T-Rex Airwolf
Align T-Rex 600N Sport
Align T-Rex 600N Pro
Align T-Rex 600e Jetranger
Comming Soon - Graupner AS350 TwinStar