Your first problem is understanding what the term 'cgminer' means 
The cgminer you get from bitmain and from *hash is not the master cgminer, it is a fork with many and varied known ignored problems.
Master cgminer will not support extranonce for a number of reasons, including we don't support alt-coins and the stratum change adds another MITM security risk attack vector.
So if you wish to avoid the, long well known, problems with the non-master cgminers - use the master cgminer from me.
But no it does not support that stratum change just for that proxy pool.
My bad, I thought I had read somewhere that the latest main branch included xnonce support (what can I say, I like beer). Anyway, I went ahead and installed your latest version for now and it seems to have overwritten the custom asic-freq file that included several other frequency settings up to 281MHz T_T Now, I realize I can manually set my freq/voltage (in fact, I am now doing so since I can't find a backup version of the asic-freq file I had before), but I have no idea what the regdata value (which is the 'freq_value' lines in the aforementioned file) should be for the frequencies higher than 250MHz. Also, what exactly is the "GH/S(paid)" column that gets added to the status page? Is it supposed to show my effective poolside rate or something? At any rate, your version is running smoothly, but I'm still not quite at the stable @ 500GH mark that I'm aiming for. Here's a screenshot of my current status for what it's worth.http://i.imgur.com/83ddM2i.pngThe cgminer you get from bitmain and from *hash is not the master cgminer, it is a fork with many and varied known ignored problems.
Master cgminer will not support extranonce for a number of reasons, including we don't support alt-coins and the stratum change adds another MITM security risk attack vector.
So if you wish to avoid the, long well known, problems with the non-master cgminers - use the master cgminer from me.
But no it does not support that stratum change just for that proxy pool.
