Jordan wrote:

Using the proper solder, or maybe silver solder

Silver solder is not an option! The steel cable will anneal.
A brass nipple and _soft_ soldering the cable into works for bikes, but
300kg? Uh!

My suggestion:
Make a brass nipple, drill and file a hole in (kind of conical), insert
the wire from the narrow side of the hole, bend the cabe 180deg and lead
it back throug the hole. The hole has to be as close as possible. Pull
on the cable so that the U-bend slips into the nipple and soft solder
the whole construction.

Nick

--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...