I was going to grab the video link, but [member=66216]GoingMyWay[/member] did that already (thx!)
As for the torsion spring, I had those on my door for many years before needing some other garage door work done. The guy saw the added rails and tensioned up the spring to make it balance perfectly. It worked fine for years, but after balancing it, it likely took a load off the opener.
As for heat and cold, while we don't have long cold spells in Arizona, we do at least hit freezing, but we also exceed 100º for most of the year. It has never bothered it. Really, it's aluminum, it won't melt even if the Arizona sun tries its best.