Reletively speaking, the weight of the carraige and forks is negligable to the system. If you drive by any rental yard, you see every zoom boom in the yard elevated and extended for weeks on end, that would also lead you to believe it is a non factor. From a personal stand point I prefer forks down (as Im sure every safety officer in North America does). Why chance coming in to work on a Monday morning to find what ever was under the forks damaged due to a "newly" discovered bypassing lift cylinder creeping down all weekend.