On their website, it looks like it starts at 62" and goes longer. The Longhorn is a hybrid. Looks like a great bow, as most of Jim's bows are.
Longhorn Hybrid The handle-riser is 16" for 62-64" bows and an 18" is for the 66-68" bows. Allowing for "no stack at the back”.
The Hybrid Longbow comes with tip overlays to accommodate Fast Flight string. Also available in 2 piece Take Down.
Build time is currently 8-12 weeks.