RoundedCornersExtender - postback flashing

I get 'flashing' when using the roundedcornerextenders

It's as if the style get's applied after the panel is loaded, which causes the panels to make a strange 'shift'

Any workarounds ?

Nothing? Where can I get official support for the toolkit?

I need to make a decision here on a project whether to use the toolkit, it all depends on support.