I fish 15 to 20# mono off canon downriggers. I get essentially zero blowback on my mono. I use scotty or the heavy duty black clips. I usually make a loop in my line before inserting it in the clip. When inserted the loop sticks out one side. I keep good tension on the mono the whole time I'm letting line out. Once down I usually don't even have to make a couple turns on the reel to get slack out as I didn't allow slack to occur on the way down. Whenever I see blowback it's always because the fisherman isn't keeping tension on his mainline when lowering the rigger.
The other negative I see to braided lines is if your fishing in a crowded area (most summer king spots are that way) you will eventually have your fish run under someone's boat or wrap with someone else's line etc. In these situations the mono is more forgiving because of the stretch. I have seen people with big kings on braided lines in these situations and haven't seen one boated yet.