Mark,
Same here. I use the v-nailer almost all the time, and the vises when I have that difficult frame. Also United is great to work with, I hope you didn't get hte wrong impression from my previous post. The vise I got from them wasn't up to my standards and they took it back. I'm sure the vise was adequate for most, or United wouldn't sell it!
If I were to buy a back-up vise I think I would go for the bigger jawed version. Meaning get the ones that can take a 6" moulding. They weren't in the catalog when I got the 2 vises (I don't think they were at least!).
But I do stick by my caveat, if the jaws are held in place with cotter pins I woldn't buy them! I'm too tough on my equipment and I know it so I have to buy with that in mind!