The very first one, "elements.txt" gives length and distance from the rear (reflector) element, which is datum zero. Distances are center to center. The fractional values in parentheses represent the decimal values in case you need them. I also have the corrected lengths for the 1.25 aluminum boom, so if wood use the middle and aluminum use the far right. Also, keep in mind these elements are 3/4" OD aluminum, which is what enables the high bandwidth and I suggest you stick with same because the design is fairly critical and required a great deal of experienced tinkering to obtain the desired performance envelope. I use 3/4" aluminum tube bought at the hardware store, and for the split driven element center support I take a 6" length of 3/4" hardwood dowel and turn it in the lath to the ID of the tube, leaving the center 1.5" at 3/4" where it passes through the boom, then sealing it with lacquer or varnish. Don't forget to put a cap, wooden or epoxy plug on/in the top driven element so it does not fill up with water. A single SS sheet metal screw 1/4" from the driven end of the elements both attaches the feed lines and secures the element. Make sure you go to the marine store and buy marine grade, heat shrink ring terminals and SS star lock washers for those connections, followed by a liberal dose of spray lacquer over everything after final assembly.
Speaking of feeds, as I said you can probably do fine attaching RG-58 directly to the elements, but if pattern consistency is important across the band you really should feed it balance by use of a BALUN, which for this antenna can be nothing more than a "Y" made from a quarter wave (15.6") and a three-quarter wave (46.8") section(s) of RG-58 with the two center conductors driving the elements and the shields grounded together at the boom/dowel cross bolt. The whole thing can be enclosed within the boom if you want since there is plenty of room to pass RG-58 past the reflector element inside, just pop the two ends out a hole just short of the driven element, attach and seal everything up. The way I do it is a bit exotic due to a marine environment and preserving the option of having alternate BALUN tuning or repairing lightning damage without removing the entire antenna. That assembly is a 3/4" copper tube with an "N" male bulkhead connector on the input side where the hardline connects, an internal "N" male connector forming the center of the "Y" and the opposite end capped with with two through-holes for the two coax lines, shield folded back and soldered to the outside of the cap and the center conductors and the entire top of the cap encased in epoxy.
One other important thing about feeds... the dimensions for the driven element are the total length, which includes the length of the feed pigtails from the point they leave the coax shield, so it is very important that you make these leads identical and as short as possible, going directly to the element, and final-trim the elements to specification. There is no boom correction factor for the driven element because it does not pass through the boom.
Regarding the boom, it is 1.25" OD aluminum thin wall tubing. After drilling pilot holes at the proper locations and enlarging them to 3/8" I use a two-piece Greenlee punch to punch them out from the inside out... shoving the punch down the inside of the boom with a rod, lining it up with a philips screwdriver and threading the punch draw bolt in from the outside. A single SS 10-24 screw through the boom and element holds things in place, you square it up and then use a center-punch to ding around the boom holes to tighten up the fit, or you could put a fillet around the joints with some PC-7 epoxy or get a buddy to drop a couple spot TIG welds.
It's a very nice antenna, and if you build it... the signals will come.