I also much prefer the B6 in terms of playability to the B7 - it seems more expressive and easier to use subtly. The B6 is held against the body by string tension by the way, so no screws in the top.
On the up side, on my two guitars the upper two screw holes for the original trapezes matched those on the B6, and I used a straplock button with a long screw in place of the third screw hole, so there were no modifications made to either guitar. The 330 worked perfectly, the Casino was much more marginal and took a lot of fiddling to get set up as I wanted it, but it's ok now. I have B6s on my 1965 ES-330 and my '90s Japanese Casino. This leaves you with a very shallow break angle over the bridge or, if the neck set on your guitar is on the shallow side, there's a chance it may not work at all. The B3 and B6 are worth considerimg for a Casino but they're designed for guitars with traditional archtop bridges as you might find on a Gretsch, rather than the 335 style bridge that sits much closer to the body of the guitar.
