I know this thread is a couple months old but I wanted to add in my two-cents here.
Using a 2TB drive is very much an option as I am doing so as we speak. Setting it up is pretty much the same as setting up any other HDD. Follow the installation guides for FMCB and on the installation window, press (R1) on your controller and you'll see a second option to install FHDB. Once completed, the PS2 will load without taking any space on your memory card. I will add that WinHIIP is the primary method of manipulating your HDD, however it does not support 2TB drives so you'll want to use "`hdl_dumb" instead. Using hdl_dumb and Open Loader Manager will allow you to do anything you need to do.
I should also state incase you don't already know, but it should go without saying that IDE drives are not 2TB so you'll need a PS2 Network Adapter that uses SATA instead. If your Network Adapter is a "clone" and not the original, you have a 90% chance of running into problems. My suggestion to resolve this is to do what I did and buy a normal IDE Network Adapter then find a SATA converter kit (Green PCB, not a purple one) and manually swap the hardware inside the adapter (you will need hex keys to do this). Once finished, you will no longer have any issues.
