[amsat-bb] Elk Ant/ metal mast??

I think I'm going to get a used Elk ant to mount on top of my 20ft tower or at least would like to. It would go on the top of the lil 20ft tower and 5 ft above it would be a 9 el 2m yagi. The mast is metal and I'm wondering how to mount it to the mast and mostly will the metal mast work ok???