[plt-scheme] Profiling Contracts

Hi all,

Is there a way to profile the time taken checking contracts?
I have used contracts heavily in some parts of my model checker, many
times checking things that are more than simple type checks... and would
like to know if there is an easy way to know, 'hey for this exection, 5%
of the time was spent checking contracts'. If there is nothing
implemented to do this, are there any guidelines on how to find an
approximation of this value?

Cheers,

Paulo Matos