I based mine on those instructions as well, except I used nylon buckles instead of the D-rings, and I made mine with solid colors, rather than two-toned. Also, I did a king cobra weave on the handle portion, to make it a little more substantial in your hand.
You also need to make the cores for the side pieces that wrap around the roll bar a little longer to fit a JK. For my JKU, I found that they needed to be 37" for the front, and 41" for the rear. Total cord for each handle is as follows...
2 pieces either 37" (front) or 41" rear for rollbar strap cores.
1 piece 50" for handle core.
2 pieces 120" for rollbar strap wrap.
1 piece 120" for handle wrap
1 piece 130" for second handle wrap (king cobra)
if you want the two toned look for the wraps, you need to have 1 60" piece of each color melted together to make the 120" lengths.
Here are the cores with the buckles attached.
Wrap done on sides, and first wrap done on handle.
Detail shot of second wrap on handle.