Coupe owners check your rear side window seals
These leak and the water runs down behind the trim and under the back seat .When you brake the water rushes forwards , goes under the carpet and forward to rot out the panel below the pedals. My RH had at least a gallon under it .
Undo the two holding bolts and pull up the rear seat squab. If you find water remove the side trim and hose the outside ....a very fine trickle will run down the inner metal panel

 

Thanks, next on my list once I finish the front door seals.

So looking forward to it...