87 924S strange passenger foot well leak
 

I understand that this is a common issue and that water in a passenger foorwell usually originates in the battery tray. I have this car gutted, so no carpet and I can clearly see the water pouring down after some rain, so I dried everything off and poured some water in the battery tray and sure enough a small stream of water leaked into the passenger foot well. What I can't understand is where the water is getting in from. I thoroughly cleaned the battery tray and though there is some surface rust, there are no holes that I can see. I understand that there are two battery tray drains, the big one pointing to the front and a smaller one on the fender side. The big one is clear, I put a wire in the small on and it's clear too, I also checked that seam just outside and under the big drain on the firewall in the engine bay and there is no leak coming from there. Ive read that plugging the small drain will remedy the problem. I'm kinda stumped.

In the dark, lay on your back looking up at the bottom of the battery tray while an assistant illuminates the compartment from above with a flashlight.

Tried that, haven't found anything yet.
Where does the smaller battery tray drain go to? I've red that it's supposed to drain to a tube in the wheel well but I just don't see it. I put a long wire into that drain and it goes into the frame rail, at no point did this wire exit anywhere I could see. I'm 100% sure now that this drain to nowhere is causing my foot well leak. If it comes down to it, I'll block the drain off but would rather find out where it's supposed to drain to and make that happen. Any ideas?
​​​