This seems to be a common problem with Vipers. Many owner have garages so it not always a concern. I have water issues also that I've been working on. Most of my problems as been on the passengers side. The plastic behind the door panel has been a problem. Water easily gets in past the plastic if not sealed well. Check there. I still have water coming in past the seal after trying RTV and roofing sealer. Neither have worked. My next try will be weatherstripping adhesive.
Also, I have had water come in under the plastic trim in the front corner. The industrial calking had a pin hole allowing water to come in under the trim and into the foot well. I sealed both sides of the car with silicone sealant. Also, my passenger side window has a gap between the rubber seal trim and the window. I think that allows too much rain to enter the inside of the door. I now lay rubber from a wiper blad in there when I know it is going to rain.
In addition to what I stated above, I also, sealed the windshield rubber gasket all the way around with RTV, sealed the bottom of the windshield (removed crowl), put RVT in the inside door hinge rubber trim piece that meets the metal and put flowable clear silcone on the sponge material on the heater core.
I think that water is also dripping in past the top back corner seal when it rains hard and getting the behind the seat wet. I know the passenger side door is sagging on the hinge, so I soon be adjusting both doors and hopefully fix that issue.