I decided to trial the security of a bowline today by trying to 'tow' a parked car
I tied one rope end as a bowline variant (mine) and the other end was a standard AGH. The trial on my bowline went well, however the gripping power of an AGH is what I was most impressed by: I snugged the AGH nub, however I deliberately left it away from the u-bolt. It stayed where I positioned it and it tightened so much as to start 'melting' some rope threads together after load.
Without wanting to break my rope (or damage my car) one would think there was a reasonably high amount of rope tension generated during my trial. I untied both knots quite easily, though the final twist of the AGH was a little stuck together.
Cheers,
mobius