I am currently on the fence whether to keep the hook keepers or to change to a foam spool cut from a pool noodle (yes!).
The hook keepers are great if you want to wind line quickly but they will kink up fluor carbon lines a bit (nothing that you can't stretch in less than 20 seconds though). Also, keeping the fly on can pose some issues if you'd put it in a backpack (get stuck, crush the fly). The foam spool is very light and can be pushed down the collapsed rod onto the grip.
Tight Lines, -K
Foam Line Holder - left one is a Level no. 3 Fluor Carbon line, 12ft. and right is a TenakaraUSA furled line, 10.5ft.
Fuji Hook Keepers