What this guy said:
A few things you're going to have to accept with the mustang that are just par for the course.....
1. do not downshift unless absolutely required.......and even then don't make the move until you match the gear you're going to by 10. As in, don't downshift to 3rd until you are at roughly 30mph.
2. limit yourself to no more than half throttle unless driving perfectly straight in rain
3. likewise try to do the majority of your braking in rain while perfectly straight.
4. if you know you're about to go through standing water at speed......feet off the pedals, both hands on the wheel.
Also, I bought some new 285's in the rear and coming from stock basic 215's it certainly helps, but not as much as I would have thought. If you upgrade your tires don't let you confidence get too high. I have great hydroplaning resistance on my new tires, and great lateral grip on turns even in the wet, but I"ll still break lose if I give it too much gas or if I"m at too high of an RPM. Just to test the other day the road was just a bit damp from a rain a few hours ago, I down shifted and gave it about 5k rpm at 70mph, still had some easy spin. Know your tires!
2012 Black V6 Coupe Auto 2.73
BAMA 93+ Race Tune, Magnaflow Comps, 3370lbs
SVT Drift 18", Nitto NT555