First, the best place for Miata information is Miata.net, the online home for Miata owners interested in basic maintenance, dropping a V8 in, and everything in between.
Now, the top is not leaking. Instead, the car has a series of drains that channel water off of the top and down to the roadway. These must be cleaned regularly. If the caller were to feel behind the seatbelt tower on the sides of the parcel shelf he would fine two plastic reservoirs with a drain at the bottom that is certainly clogged. Using a test-tube brush, or something similarly long and thin, clean out the drain and the water will find it's way to the roadway. There are also tiny openings in the pinch welds under the doors that must be kept clean so that water can drain from the front drain system.
Right now water is overflowing the drain reservoir and collecting under the seat where there is a raised ridge that the front of the seat rails bolt to. It will act as a dam to prevent the water from coming into the foot well, until he brakes hard.
Clean the drains, dry out the interior of the car, and maybe clean out under the seats where water has been collecting. Do this now and the car should last for many more years.
Chesapeake Area Roadsters
I wish Tom and Ray would learn a little bit about these insanely popular cars.