I started a thread a few weeks ago about the DD mod since I was doing my clutch. Well, I am running the full Barnett kit (frictions and plates) and the DD mod with doubled up springs.
Holy Mother's Bunions, this thing is stout! I should probably do braided stainless hoses pretty soon. I'm sure it's taking more pressure to activate the slave now.
It may be too much for my urban street-fighter deployment, but I'll give it a few weeks. If my left forearm starts looking like Popeye, the extra spring is coming out.
Also, somebody said it makes for a binary clutch (on/off). That is very true and takes a bit of adjustment. But, for damn sure, when engaged, it's REALLY engaged.