Maybe go for buildings that are a little more accessible (wider) for tanks to fit in like a warehouse from the Tutorial mission where the infantry can easily see? some designs that could help it a little easier on your load before you would refine them once the major ones are dealt with.
Also it may be more dangerous since its often on the enemy's perspective during our offensive operations so its like a PEEK-A-BOO thats often used by them rather than us in defensive missions. but then again you can always make a new mission that involves alot of garrisoned tanks, also what are the chances of a HULL DOWN enemy tank during our sweep?