A trick to tighten the window traditionally known as a "wind wing" by old timers: http://www.thesamba.com/vw/forum/viewtopic.php?p=2623898&highlight=wing#2623898

This may not last long, but it's easy. 

Stuart

] On 
> Behalf Of Gnarlodious
> Sent: Monday, June 09, 2014 10:28 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Triangle vent window question
>
> My window opens all the way ('83) and I get a good breeze in my face 
> except I have to hold it in position. Is there a friction adjuster to 
> keep it open fully while I am driving faster than 30MPH?
>
> -- Gnarlie