Servo won't work... 17kg is rated at 10mm from the centre of the output shaft... Devide that over the length of your arm or whatever your having and the force becomes pretty weak.

360s setup is pretty complex due to it having to fit in a wierd orientation... Astroflight coupled to a custom 2 stage worm reduction and a 3rd stage spur gear setup giving it 900:1.

Glens robot deamon in aus has a pretty slick setup that works well... I'll let you google it.

Maybe one of the lowest geared banebots planetary p60 gearboxes could also work.