There are some at
http://www.football-freaks.com but most of these guys seem primarily concerned with coach mode or CPU vs CPU sliders. Otherwise, I'd expect any good PS2 or XBOX sliders to be a good starting point on PC since they run on the same engine. Personally, I've started a franchise on default All-Pro and I'll probably adjust after a season or so. So far it's been pretty good through 3 games.
One thing I really like about the PC version is that if you turn the cone off, it's off for the CPU as well. I've never been a fan of the cone for myself and it used to screw up the CPU's passing too. I remember having to switch the controller to the CPU team for one play every game on PS2 and XBOX to be able to turn the cone off for the CPU.