All performers or any pilot in the airshow has to be certified to fly in
waivered airspace.

I assume these pilots hold FAST cards in the very least. Other FAA
approved formation organizations are TRARON, FFI for the RV's and others
like the liason group that started it all. IIRC

The bible for all these groups is the T-34 manual.

The latest iteration is called the Formation Flight manual 4th Edition
sold by the EAA for $14.95. "now includes T-6, T-28, & P-51"

The TYPE SPECIFIC: P-51 Mustang page is page 26. written by Vlado
Lenoch

" Pitch and Landing: The leader will configure the flight as
appropriate for the break. Runway width will dictate the break
interval. On runways that are 100 ft. wide, the spacing can be as close
as 1600 ft. as aircraft will be landing on alternate sides of center.
In no case should any airplane land closer than 3000 ft directly behind
another. The leader will bring the flight over at the appropriate
speed, so that after the break, all aircraft will be able to end abeam
the point of intended landing at 1000 ft and at 170 MPH (147 KTS), where
the gear is extended and the turn to final "played" to fine tune ay
spacing.

Section landings are not done in P-51's due to control and visibility
limitations."

FWIW