Assuming that you are using POST as the method in the form, then you shouldn't run into any problems with the size of data in your input (hidden or otherwise). The limit is purely enforced by the browser... use a different browser/operating system -- and you may experience a different upper limit.
If you are using GET as the method... then the size limit will be greatly reduced (to between 256 and 1024 characters in my experience).
Hope that gets the ball rolling for you,
Jeff