Everytime i have the farm mission where i spawn in the lower left corner and the ship is in the middle right i have problem completing it because aliens can shoot through objects. I am asuming that the way the rear of the heli is facing the top and the front of the heli is facing the bottem, just for clarification.
1 Landed/crashed alien ship: Aliens who are 'in' the ship shoot straight through the walls even detecting those outside of the ship on the sides and the back. Futhermore most of the time (i had 1 time that the ship had walls and an interieur) the aliens and myself can walk straight through the ship.
2 Hedges: all of the hedged can be shot through by the aliens, making it almost inpossible. I tried this tactic myself, having soldier spot the alien and have the other behind a hedge to shoot him. I have found that a rifle shoots just fine through the hedges while the sniper/precision rifle will damage the hedge, i havent tried any other weapons.
3 Barn: There is a barn on the upper right corner of that map. The barn has walls where both the aliens and myself (rifles only so far) can shoot through.
There is also a problem where 2 bales of hay spawn in my heli and is preventing people who spawned on that spot to be able to move.