Place them in any ordinary microwave for approximately 15minutes, if they're still not small enough then try a further 5mins. - & so on.
The microwaves will affect the polymer molecules in the frame reverting it back to it's original molded form (due to all materials having varying levels of 'memory').
Once they're how you wish them to remain, quench the frame in a bowl of mashed up banana's. This will align the tiny fibres in the material of the frame, & help to keep the new shape.
Bob BB, October 2008