I'm also experiencing choppy performance every now and then in my map (especially with Windows 7), but it may also be the number of destroyable targets I have in the map. I think the number of dummy soldiers is near 200. I'm told by the bfeditor.org guys that usually a map can take up to 100 destroyables. They also say the destroyable objects may not lightmap properly. FH2 however can take up to 350.
So I might consider reducing the number of dummy soldiers if it can improve performance. I might reduce the number in the shooting range and urban combat area in the Axis Training Area. I would do the same in the Allied Urban Combat Area.
I might also reduce the number of walls and barriers by rerouting the big barriers just to surround the barracks and training areas on both sides while leaving the combat zone wide open.
Maybe I should use 3ds max to do the lightmapping.