I just picked up a Betson 27" monitor and was getting ready to mount it. Luckily there were already pieces of wood inside my cab (complete with bolt holes) to mount the monitor. However, the mounts are for a 25" inch monitor and they have to be moved slightly to accommodate the larger 27" size. I haven't made the modifications yet, so I can still take pictures of the monitor mounts as they are. Unfortunately, I'm not at home at the moment, so I can't right now.

However, I will post the pics as soon as I can. In the meantime, I will try to describe it. Basically, for the top part of the monitor (3 bolts) the cab has a block of wood on the left and right side which is screwed in from the inside of the cabinet. (The screws used do not go all the way through to the outside) Then a piece of plywood is screwed into those pieces and goes all the way across to either end. On that piece of plywood is 3 holes with bolts. The monitor then bolts into the plywood. The same is true for the bottom.
Since the cab already had these pieces of wood in there (originally from when it was manufactured) I'm pretty confident that they are strong enough to hold the monitor. However, since it's a 27" and a bit heavier than the original 25", I plan to also put pieces of wood or brackets under the monitor for additional support once the monitor is mounted.
Again, all of this can be accomplished by screwing in small pieces of wood from the inside of the cab without having to have an unsightly bolts on the outside of the cab. The screw should be long enough to make it through the wood you are screwing to the cab, but short enough to not go all the way through to the outside. When I post the pics I will also include the size screw I used.
** UPDATE: Pictures posted **
(excuse the wood filler - I'm preparing my cab for painting)
~ DeLuSioNaL