atheros ack timings...sysctl?

Hi,

I have just cvsupped the latest current sources and made world...
But I wonder if it is possible to change the ack timings in atheros 
hardware? I have been going through the mailing list archives and it is 
mentioned that this might be done through sysctl but I couldnt find any 
such variable to change ack timings of atheros.

This is possible with madwifi drivers as it seems but the required 
patches hasnt been applied to freebsd?

Thanks
Evren