I am not familar with this furler
. However,it may be helpful to run a messenger line
inside the "luff-tube" (probally not the right technical name) to attach to and guide the headstay, espically if the headstay isn't changed -remains attached to the mast.
When I installed my furler
I tied a large knot in the end of a string. The knot was small enough to fit inside the RF and the string more than long enough to trave the length. With a friends help, I feed the string into the luff-tube while he used a vacuum to suck from the other end. After the string was drawn thru I attached the largest (strongest) line
I had that would fit insid the luff -tube then tied off the to the head stay at the tack. We then used the messenger to help pull/guide the headstay as we slid the RF up to the top of the mast.
This is a technique similar to what electricians use to draw a messenger into conduit before pulling wire.
Even if you install a new headstay, at ground level, this may be helpful in getting the wire into the RF.