HokieBGE,9 men & 9 women. Depending on sides and how hungry? I'd say at least 4 racks for the guys and maybe 3 racks for the girls. Including some for left overs and pre party testing. I'd go 10 racks. No problem fillting on the XL just stack them. If you'd like to do 20 racks on a LGE see link.
