Europa-List: Eyeball Vents

[Tony Renshaw <tonyrenshaw268@gmail.com>]

Gidday,
I have a fitting in my roof panel that accommodates 2 x 2" gauges, or now I am
wondering about incorporating 2 eyeball vents, and incorporating Nigel Charles's
roof ventilation mod.  The holes are 2" in diameter and there seems to be one
vent to suit at Spruce, albeit it is expensive. 
http://www.aircraftspruce.com/catalog/appages/roundvent1.php
Has anyone used these high quality eyeball vents and do you have an opinion I 
could
be privy to??

Reg
Tony Renshaw
Sydney Aussie