In the menu data .js files, the _subOffsetTop and _subOffsetLeft constants serve a very useful function. However, after angering myself for a little while, I realized that these have no effect in the horizontal arrangement of the board. Looking in mmenudom.js and mmenuns4.js, I saw that these offsets are only added in if(!horiz). Modifying this was easy (I added 2 more constants [_subHorizOffsetTop and _subHorizOffsetLeft], and made the appropriate modifications in the dom and ns4 files so that these offsets would be taken into account where appropriate. Also, Opera7 was rendering the submenus of horizontal menus 10 pixels "too high" and "too far left" compared to IE6 and MozFirebird 0.6. It seems taht there is a relatively simple solution along the lines of if(op7) _top+=10, _left+=10. I haven't had the opportunity to "check" these values in other versions of Opera, or in the same version of Opera on a different computer, but I thought I'd give the information based on what I had thus far.
Also, as an unrelated (and relatively unimportant) aside, the dom.js and ns4.js files in the RC3 download still are commented as belonging to RC2. Just FYI.
Thanks,
Edward