or is this a FPS issue?
It's definately possible, I'm trying to get it worked out for Crete. Just gotta be careful and space them out enough. So you couldn't really do a dense area, but you can get the basic idea ingame...
Couldn't you just make a hedgerow model and place it down instead of actually using the fona in game?
Though i wonder if you can code it so only allied tanks with teeth can go through it and all other vehicles cann't (but infantry of course can also go through albiet at a slower speed).
you could make hedgerows like sand bags.have a small section and place them side by side.