The images in the post from Edward Kokoski show the track locations of the working jib, not the blade. Those tracks are quite a bit further aft than where the blade tracks should be located. The working jib is a smaller headsail whose high clew needs tracks positioned further aft.
In my opinion, the blade is a much better sail for day sailing, singlehanding and for shortening sail in windy/flatter sea state conditions.
For accommodating only the blade, the middle of the blade tracks would be on the "sweet spot" for the lead cars, with the same amount of track forward of the designated location as aft. However, the rule states the tracks can be extended aft to accommodate proper lead position for the working jib as well (two tracks on the cabin top instead of four...):
"Blade jib sheet lead blocks shall be confined to the cabin top. The tracks for these blocks shall
be no less than 16" long and may be extended aft to accommodate lead blocks for the working
jib. The athwartship center of each track shall be no more than 17.5" abeam of a point on the
centerline measured 7' 6" aft of the foremost stemhead-fitting hole. Each track must be aligned
toward this same hole. The track position may be adjusted up to 1/2" forward or aft to avoid
drilling bolt holes through the cabin top ribs."
Measure 7' 6" aft of the foremost stemhead hole (which will be just in front of the partners), then measure 17.5" directly athwartship (90°) to either side to find the "sweet spot". With that location marked and with 16" tracks, the middle of the track would be placed there, with 8" in front and aft of that position.
I snapped a chalk line secured at the foremost stemhead hole, which passed through the "sweet spot" mark to ensure the track pointed in the correct direction.
Be sure:
1) Your track mounting holes and car adjustment holes are the same from side to side.
2) The mounting holes miss the cabin top ribs inside the cabin (stiffening gussets).
3) Mount the tracks using butyl tape and the recommended method of mounting deck hardware (countersinking the mounting holes to avoid spider cracks and enhancing proper sealing.)
https://marinehowto.com/bed-it-tape/
Best regards,
Bud Brown