The handbrake on the F and TF is just about adequate when it's working properly.
The usual culprit is the levers on the rear callipers seize up, meaning that all you are doing if you heave on the handbrake lever is stretch the cables.
first thing you need to do is identify the problem, so you need someone under the back of the car watching what happens when the handbrake is applied. Pound to a penny the levers don't move.
You can free these off temporarily by applying something like plusgas and tapping the lever, but normally the real answer is new or refurbished callipers.
But find out if it is the levers first and come back to us.