1. Look in the Modifications forum around May 2006 for a thread titled "Sail Slugs."
2. Look in the Performance forum around May 2006 for "Reefing with Sail Slugs."
My dealer's option for mainsail slugs included jacklines on my sail, but wish it didn't. Dealer Bill (of Boats4Sail) posted his suggestion of slug spacing that obviates jacklines. It is possible ... but you can't assume anyone's advice will address your individual situation. Especially if your sail has two reefing points, each sail could be spaced differently.
But everyone can make sure that their slug spacing is mapped to match their own reef points.
Reef points on a 26X might be at 42" and 84" from the tack grommet. Draw only the bottom half of your mainsail on legal paper, scaling the drawing at one inch per foot ... probably 14" for your 26M (or 12.5" tall for the 25' sail luff of a 26X).
Ignore the upper mainsail where slugs can be equally spaced. Mark your reef points to scale, mark your slug-stopper at ~8 inches above the boom, and plot how the sail will fold. For the 26X (42" and 84") fold it like a paper doll so the bottom 3.5 inches of paper can place first reef "at the boom" and so the last 7 inches will place the deep reef at the boom.
It's pretty simple to see how slugs can be mapped for slab reefing to match YOUR reefing points. There isn't necessarily a measurement that will work for every sail. However,
every mainsail can be mapped for slugs that permit reefing without jacklines, while the slugs remain in the track. You can prove it to yourself by plotting Bill's measurements on a drawing of the 26X mainsail.
For example .... in order to bring the 42" reef cringle down to the boom (slug-stopper at ~8 inches), the first slug can be at 9" next at 30" followed by next slug at ~10 inches above above that reef point, say at ~52 inches. So for a slug-stopper at 8 inches, slugs must be at least 10 inches above and below the first reef cringle. The gap must be larger, say ~15 inches above/below the second reef cringle. (Calculations should assume that the stopper is two inches higher than its actual position.)
Anyhow, just one opinion ... read Bill's advice closely, ADAPT to your own sail, & avoid jacklines.
I've pondered making a simple scale drawing in easyCAD that depicts the reef points, the slug stopper and sail slugs - but never found time. Someday, somebody will probably do that and post the drawing under MacMods.