My take would be it's not worth running below the gnar to the mouth at 200. I think the lowest I've done below the Gnar to near VSmith is ~250 which ended up with a cracked boat above the dam. It was fun, but definitely boat abuse. Granted the air temp was near freezing and the ice added to the entertainment factor. 300 and up is nicer as you hit fewer rocks. 400 is even better.
VS to the narrows I really don't like below ~400ish. The Narrows the lowest I've done was at ~200ish, but that was a guess at the time. Boatable, but not that great. Got some dirty looks from fishermen as we came around one corner.
I'd guess 200 would be on part with the first trip down the Little South Lenny.
"Basic research is what I am doing when I don't know what I am doing." -- Werner von Braun