Give me a Dyna-King anyday over a Renzetti!! I have never been very impressed with the frail nature of the Renzetti nor the difficult of use and the less then perfect hook holding power.
I have yet to figure out what is so great about them....maybe someone could fill me in.
On other hand, the Dyna-King's are easy to use and hold a hook like no other vise. The Kingfisher is a great vise for the money and have not came across the problem you mentioned although I have only played aroudn with it and have never tied on it. If you are worried about that problem, pick up the Squire which runs about the same price as the Traveler.
Also, on the Kingfisher, the vise CAN be unscrewed from the base. That is how they ship 'em!