I ended up doing something similar last time. Usually just putting them in the car and putting it back on the ground will do it though. Once you get them fairly tight you should be able to use a torque wrench and have the shaft stay put.I just installed Epic springs a couple days ago ... I also had this issue. Are you trying to torque them to spec .. or just tighten them? What i did was take my 14mm socket and used a vice grip to hold onto it. Put it on the top hat bolt and then I put the allen wrench through the middle of the socket and tighten it that way. It worked well!