Wall-Glitching/Collision Glitching from a roof

Video: Wall-Glitching from a roof top. (PERSPECTIVE 1)
http://www.xfire.com/videos/5afd0a
 Wall-Glitching from a roof top. (PERSPECTIVE 2)
http://www.xfire.com/videos/5afd0b

What is it?: This happens when another player is standing on top of a roof firing at another player below. The shots from the weapon glitch through the edge of the roof hitting the player below. As a result of this players on roofs are able to kill players below them however it's not possible for the player to damage the player on the roof back from that angle.

Why is it a glitch?: The rounds from the person on the roofs weapon glitch through the solid edge of the roof. The player on top can see the player on the bottom however the player at the bottom can not see the player on the top clearly. The reason for this I am uncertain I believe it has something to do with the positioning of Vice City's camera in 3rd person and perhaps the height of reticle being higher than the actual player model combined with a "If you can aim at it with the cursor you can hit it" system ingame.

Allowed ingame: No, do not do this. However, this can be easily done by mistake in a fast paced situation. Instinct tells the player that if they are standing too close to the edge of the roof and are being shot at from below too move back away from the edge. Some players may not even realise they are doing this therefore admins should be more forgiving when a player does this.