I've taken to making machines horizontal. The best air coolers now exceed 1200 grams (~2.6lbs). Having this leverage sideways on the mb is ugly enough, but it really makes keeping good contact with the CPU worrisome.
It could be offset by a "strap" of sorts, although I've never seen one available commercially.
On review sites I often see several reports about excellent coolers where the user is claiming it's "worse" than the stock cooler. Every time I envision this heavy cooler cockeyed bending the mb and losing contact.
Now many cooler manufacturers recommend removing the cooler before moving the PC, yikes - that is a lot of extra work.
Anyone else have an opinion?