I've stacked as many as 3 racks on top of one another while doing an indirect cook on a gas grill.
Figured they tenderized each other.
I usually don't do that many racks at the same time anymore.
New Braunfels Hondo Offset
New Braunfels Bandera (Refurbished & Improved)
33 year old Char-Broil 450
1996 Blue Weber SS Performer
2003 Black Weber SS Performer
Weber 22.5" rotisserie & Smokenator system
Weber SJS & modified stock pot Mini-WSM
STOK Island gasser
Recipient of Official & Un-Official Moink Certificates