Don't you have to display the Heights buildings to keep the real estate value? I have ZERO room in my SH area as it's taken up by SH buildings everywhere. It looks messy and I hate it. If I stored everything, I'd have way more room to build regular houses and stuff without having o buy more land, but as I said, I assumed that doing so would take my value (and hidden multiplier bonuses) down.
Last question - do trees count as items toward your maximum? I keep getting warnings that I have over 7100 buildings (right now I have slightly over 7700) and the game may not run as well. However, I design my city as realistically as possible and as such have many, many trees. If I sell or hoard some, can I drop back below the warning limit?