I FMQ'd a large king (120 x 120) on my 6600! You can totally do it! It really wasn't that bad at all. I didn't quilt in sections or "as you go", it was a standard/complete quilt sandwich that I just shoved under the needle.
I do the "puddle" method too. I have tables behind and to the left of my machine table, and my machine is set down into the table. All of that helps manage the quilt weight, but you can get by with your extension table and some creative use of things like ironing boards if you don't have a setup like that.
Grippy gloves help immensely, as well - I can't quilt without grippy gloves of some type.