Topband: 1/4, 1/2 or 5/8 Wire Vertical Which to use??

[Richard Cariello]

Hello to all,
I am going to fly a Wire Vertical for 160 meters. The wire will be held up with the use of a Balloon. I have done this many times before. My question is which antenna length should I use,1/4 1/2 or 5/8 wave lenght. The Vertical will be ground mounted and feed at the base.The location will be on top of 300 foot hill in Staten Island NY. The soil is clay with rock. I will be laying onto the ground six or eight 1/4 wave radials. The location dose slop in all directions.
Thanks for your help,
Rich AA2MF