dirt,
I've used both FEL and frame mounted plows, and both have advantages. With my current tractor I don't have a choice so I use the FEL blade. It does work better with the longer reach to push snow further accross the ditches, or into drop-offs if needed. It also works much better to push snow into tall piles and out of the way.
There's a lot of discussion about side pressure on the FEL arms, but in my case I haven't noticed much. I got to experiment quite a bit Saturday with a over a foot of snow. I found if I kept the blade edge slightly above the surface, or when resting on the skid shoes, the tractor had no side push at all. I could drive for 100' with my hands off the steering wheel and it would hold a straight line most of the time. This was done on the gravel part of my drive. But, when I scraped the blade edge to clean the concrete portion, I had to compensate for a slight side push most of the time. That seemed to depend on the amount of ice packed to the concrete under the snow layer. One time I had to brake steer to hold a straight line on the concrete.
One thing that helps my setup is how the blade floats. If you build the FEL blade, try to use a hinged design with check chains. That will allow you to lower your FEL until the blade is floating on its own, and have much less weight on the blade. If your blade does not float, and requires you to float your whole FEL arms, I think you will get much more side push due to all the weight on the blade.
If you can build a floating blade for your FEL, I would go that route. If you cannot float the blade I would try the frame mounted design first.
