Heater Air Duct Hose: Questions

["James_ TR6" <jattr6@hotmail.com>]

I have heard of people using this hose for the heating duct:
http://www.mcmaster.com/ : part number 53145-K33, General Purpose
Polypro/Rubber Duct Hose, Black, 1-3/4" ID and 2" OD.

I am curious if it is as "stiff" as the Original equipment?
years ago I bought some replacement tube hose from the Pep brothers, but the 
darn hose sags
too easily.

any insights or opinions?
I would ideally like the closest to Original and may just try to order from 
the big parts folks.

thanks!

James
1976 TR6
Maryland