TBH i'd be worried, too. heated plastics that aren't supposed to be heated are not a good thing no matter what. if you can, you could try getting the 75W and see how it goes, bc the direct heat does concern me.
i'm not sure of a solution to the problem with the plastic bars...i'd try the 75W if it's possible.
EDIT: what temp do you need it at to get your temps right?