I've been hanging around this forum for years and finally joined a while back. Then haven't posted anything until today! Lots of good stuff here and I thought I would try and contribute.
For those contemplating the 530T window modules in Cadillac CTS, here is what I've found that may make your job a whole lot easier...albeit more expensive. We are working on a 2005 CTS-V, so it should apply for several years.
First thing...use a module for every window. I know...it means an additional two 530T's...but it will save you a ton of heavy gauge wire routing and aggravation. This car has a door module in every door...and there is a 4 pin connector at each module that has everything you need. There is a 30A power lead, ground, and the two motor wires. These wires are heavy enough to withstand the load requirements the factory has determined are necessary, and are in fact, 12ga wire where the 530T is 14ga if I recall. Take the connector apart so it's easy to work with the wires, solder and shrink wrap. Since the power feed is fused by a 30A circuit that is factory rated to control the window motor, it's more than enough for the 20A requirements of the 530T. We simply mounted each module next to the door module, and soldered our connections. You are using less than a foot of the module wiring. This way, the only wires you need to run through the door and that little itty bitty door bellows are the signal wires for the module. That's a whole bunch easier than running motor wires too...and it's much more effective since you aren't running long leads that can create resistance themselves. Don't worry about moisture harming the modules on this car. The door module is there and it's a whole lot more money than the 530T...so if GM thinks it's safe, we're probably safe to assume ours is safe from water too. Especially when you see how they did it.
So although you will have an extra $100 in modules, you will save a chunk of money in heavy gauge wire, and a ton of time and aggravation fishing that wire into the door.
One draw back...if you blow a fuse, you have to pull the door panel. But that is a 3 minute job, and quite honestly, if you blow a fuse, you should be going in to find out why anyway. You could use a circuit breaker instead, but then you may not know if you have a problem until it's too late. You could also run the power feed so the fuse is exposed when you pull a bezel off the panel...but then again, you should be looking for a reason for a blown fuse.
Just a thought for those who might be interested.