I don't thing you will gain much more than what you're allready getting from a performance point of view, pretty marginal if your are allready running topless.
If you were running a higher spec motor which had a larger combination of mods over a semi standard bike(chip/pipes/cams/injectors etc) it would be more benificial, like all these things, it the combined effect of all items that make the noticable difference.
just my input graham, but I know where your're coming from .