I did it - I converted my Macomber Ad-A-Harness B5 10H 14T treadle tie-ups to Texsolv. I had a really bad problem with hooks popping off no matter how gently I depressed the treadles or whether I rode them back up with my foot or not. This was so frustrating! Especially since most Mac owners have no such issues.
I ordered the Texsolv kit from Halcyon for $90 including shipping (yikes!) - it includes a 54 yard spool of Texsolv and two baggies of different types of pegs.
I cut 13" cords. I tied up a treadle with 1 Mac hook to the furthest back lamm to function as a template, maintaining the correct height and angle of the treadle. Then I depressed that treadle, and looped the already cut cord over the lamm, and pulled it through the last hole in the cord (EDIT: Use the second-to-last hole, not the last hole), and snugged it tight to the bottom of the lamm. That secured it at the top. Underneath the treadle, I secured the cord with a Texsolv peg. The official Mac treadle hook maintained the height, telling me which cord loop to put the peg in. After I did the first cord, I removed the Mac hook. The first cord maintained the correct height and angle of the treadle from then on. I tied a cord to every lamm, at every spot where the hooks are meant to go. It's easiest to work seated on the floor at the treadles, and to tie up the farthest back lamm first, working forward (that way, the front lamms are not in the way when you depress the treadle). It's also best to work across the same lamm, doing all the treadles, before you move on to the next closer lamm. The cords will stay tied to the lamms permanently, and only pegged when needed. There's about 2 inches of extra cord under the treadle. My intention was to put a peg in the bottom loop of the cord, under the treadle, when it was in resting position. Alas, this seems to be more than my kitties can resist - they never play with strings, but apparently a loose string with a little peg on the end is irresistible. So I removed all the pegs that I’m not currently using for my tie-up, and am keeping them in a container in the castle. The strings are dangling, though they’re tucked into the resting treadle slots. The kitties are not interested in peg-less cords, thank goodness!
Now my Mac's treadling action is so much smoother and precise. It's quieter, too. And no skips or floats due to dropped hooks!
Here's a picture in my Flickr account of my Mac with his new feet: http://www.flickr.com/photos/debbie-b/5490247011/
Debbie
EDIT: Texsolv recommends that you NOT use the last loop in a cord, but rather use the next loop inward. The last loop is the weakest section, because the cut is closest to it.