biggerry wrote:the length is of little consequence
Until you try to fit in in or on your car
6 Foot will fit inside most cars as long as you have access through the boot into the passenger compartment. I can get 3m(10ft) into Pam's Peugeot 307.
12 foot will go on the roof of most cars without too many dramas
Over that will cause real headaches.
This is relevant because the most economical way to buy is usually the longest & always a standard length. This is 145 Inch (12Ft) or 242 Inch (20Ft)
But the standard length of the drive belt is 6 Ft.
So it is either buy a 12 ft rail & pay extra for a special belt, or get a standard belt and pay extra to get a 6ft (special length) rail. Though the overall cost will probably be lower.
OTOH longer rails may give greater scope for creativity. E.g. Hang one end over the end of a builiding & shoot down.
Either way I would pay extra for anodised. If I know you, you are going to want to drop it in the ocean sooner or later.
Regardless, I need to work on turning my time lapse shoots from a bunch of photos into a video. I have a few sequences taken already, but like you it is a once in a blue moon thing. (Or less frequent depending on your definition of a blue moon. There are several. The most commonly accepted definition is the second full moon in a calendar month. This type is actually quite frequent.)