I have been using some fairly large open frame, 24VDC relays that I got years ago. These are similar to the smaller Array Solutions relays.
see:
http://www.dl1iao.com/album/k3nd99/7.jpg
Although I'm not switching a 4 square, these relays have worked fine for years switching L-networks at the base of a 80/160 vertical.
73, Stew K3ND