We all know the rule that vehicles need 50% concealment to gain the benefits of cover. The G2D4 and the Game Preserve players have two different ways of interpreting this rule. I just wanted to go into the reasoning why at G2D4 we play it the way we do.
At G2d4 we play that any vehicle at least 50% into the bases of area terrain defined as forests are granted cover, and that shooting though that base grants cover to vehicles on the other side. This is opposed to the GP way that requires that 50% of the vehicle is blocked by the physical models of the trees. TLOS and the strict reading of the rules would seem to back up the GP guys, but it really comes down to how you define the piece of terrain.
If you define the base as chest high foliage with a few static trees, then, yes I'd agree with the TLOS interpretation. If you define the base as being completely covered in trees similar to those placed on the base, then the G2D4 interpretation makes more sense.
It's impractical from a gaming standpoint to model forest as we play them to work in TLOS fashion. You have a hard time placing models in terrain modeled in such a way. Instead you use the base with trees on it that indicate the type of terrain, and you can move the trees around to better allow for placing of models without effecting the cover that the terrain generates. Essentially we're saying that the terrain is a lot more interesting looking than how we've represented it on the table top. This is done for the gaming reasons above, and due to the wear an tear such a terrain piece would take for normal play. Plus its cheap and easy to put two Woodland Scenic trees on a piece of felt and call it a lush dense forest.
If you play it the GP way, I think a forest piece needs to have at least 4 or 5 trees on it and you cannot move the placement of the trees at all during the game. Also, the stump should be treated as impassible so you cannot park any models on top of the trees.
For the G2D4 way you just put 1-2 trees on the base and move them around when they become inconvenient. I think it's a lot simpler to play it this way. You have a lot less stooping down to model level and arguing about if 50% is really covered.
I don't think the G2D4 way violates the rulebook either as the effects of terrain are agreed upon by the two players.
I do think that the way it should be played should be agreed beforehand. Regulars at a particular store tend to just accept the way terrain is played by convention, and you need to make sure things are clear when you play a new face. For instance the few times I've played pickup games at a GP store, regulars liked to claim cover saves for infantry when standing on those Aquila Lander pieces from the 4e starter box. At G2D4 we tend to play them as difficult terrain that only grants cover to something behind but not on top of. I like to go off the convention of: 'Your store, your rules.' At least for the first few games until people get to know me and I can make an argument and not seem like a know-it-all outsider.