Actually I have two...

First, on repair rolls, do you roll for each critical card you have(if repairable) or only one per turn? For instance: I picked up 3 critical cards, all of the repairable, at the Command phase, do I roll a die for each card, or do I pick one card and try to repair that one per turn.

Second: Hills! Do they block line of site if behind or do they provide cover? So far we have been eyeballing it and if you can see any part the tank, you have cover.

Maybe for hills go the Battletech route. Since Tanks is a basically a three-dimensional game played on a two-dimensional board, give hills contour lines showing height. For something the size of the small Woods, maybe two contour lines (the edge and another half way between the edge and center point); for something the size of the larger Woods, three contours.

Tanks are Level 0 plus the Level of the Hill it's sitting on. Nearby hills one level greater than the tank provide Cover but do not block LoS; nearby Hills two levels greater than the tank block LoS.

Maybe allow a -1 Defense when being fired on by a tank at a higher level (to represent shots landing on the weaker top armour/thin hatches/engine coverings).

Similar rules could work for negative height terrain (bomb craters, sinkholes, dry river beds, valleys, etc.)