I've found that you need to tension up new lines to get the factory hockles out of it, after you use it for a while it develops a new bend "frequency" ad Tom D. puts it.
What i will do is set the line in a big crotch, put a throwball on each end and pull hard. The design a little stretch in the cordage, which is counter productive, I like a more hard lay in the line.
The problem with the bigger diameter lines is you get more resistance in flight, so its harder to hit those 80-100 ft TIP's. If you are going for 50-60 it does not really matter. I have the 2.2mm ZingIt in one of the huge rolls, so if I have to cut it down too far I just pull out a new section, then give the short line to a client. it is less than $0.20/ft (w/shipping) so I do not get too attached to it.
With the supper big shot on very tall trees you may wast to start with monfil as your first messenger line. I think Graeme actually uses bailing twine since it biodegrades. Having a disposable line for those really tall shots can be a time saver.