HiperLCS700 max frequence

Hi,
I intend to use HyperLCS700 at 500Khz (or higher) in order to reduce the (and use planar) magnetic parts.
We are looking for very compact PS less than ( HXL) 0.63x0.63 inch.
The efficiency must be above 90%, input voltage 108-132Vac.
The max power is 25W, PF above 0.9.
What is the maxim frequency that it can be used above recommended 300Khz
The PI Expert flag an warning that the maximum Vpeak 190V is to low,
is there an minimum voltage in order to have an stable resonant PS.