That's a tough one if you mean that you want to buy and install a furler
without ever going aloft or unstepping the mast
. I don't know of any design that would allow that. As far as I know, all designs will need to have the forestay laid out on a flat area for measuring and fitting.
As to the CDI furler
... as I recall
it is of the type with an integral halyard
. This means that there is no upper swivel to buy/worry about, and its absence reduces weight aloft. So, I guess that the foil section that they use must be heavier than other designs. Anyhow, unless you are actively racing
, that small difference in weight will likely be invisible to you, so I wouldn't let that drive your decision.
One problem that some seem to have with that sort of furler is getting enough halyard
tension on the genoa
. The sheave at the top is usually tiny and without bearings, so that heaving on the integral halyard doesn't get the sail stretched much, and on some headsails this is important.
Lastly, if you want that type of furler, there is one made here in Oz called a Reefurl (I think). It is a bit agricultural in appearance but seems to work well enough (seen on lots of local boats), and it is very inexpensive here. Don't know about in your area.
Anyhow, good luck with your decision.
Jim and Ann s/v Insatiable II lying Church Point, NSW, Oz