My impression is that slight contact during the tight formations is not
all that uncommon, and not generally a real problem - Just a bit of
touch-up painting required now and then ;o)

As far as the opposing pass maneuver, the aircraft are not lined up
horizontally, which is not really evident from the crowd line. Thus,
when they pass, they actually appear much closer than they really are.
Of course, at a closure rate of 1000mph, it wouldn't take much of a
mistake to turn tragic...

The midfield crossing maneuvers are done with a combination of site
reference points, speed control, and radio calls (from the flight
"Boss" flying plane #1). Presumably, all aircraft are flying at the
same speed, in different directions away from show center. At a
designated time/location, "Boss" makes a radio call so that all
aircraft climb (again, at a designated rate). Another radio call
signals the break at the top, where all aircraft decend toward show
center, again at identical speeds. If all goes well, they cross (at
slightly different altitudes) at show center. I've seen them get it
right, and I've seen them get it no-quite-right. )

Radio calls are used throughout the show, between the 2 "solo's" and
the diamond-guys, mostly from "Boss" - "Smoke on, ready, now" -- "Smoke
off, ready, now" "Up we go... a little more pull" "coming by show
center!" "prepare for the left echelon roll..." etc... etc... etc...

Get a radio scanner that can pick up military air frequencies, and
enjoy the show with a whole new perspective!

Regards,
Pat