I can't remember which lock number it is at Napton, but it's 2 or 3 locks up from the folly pub, it turns out is known to be slightly narrower I learned last year.
Our boat managed to pass ok without the use of tie rods (we are just about 7ft at the widest point of the old girls middle age spread) but later the same day one of the Coventry Canal Societies boat Panther (ex working boat that had been shortened) got stuck.
I think it all depends on the water level in the lock.
As I understand it, it's narrower the deeper you are in it, sort of a v shape.
Eventually Panther did get through by getting the water level slightly higher that normal by emptying a few locks above it in the flight first and then filling it....
Hope this helps/makes sense