Here is the Hy-Gain LJ-105CA 5-element 10-meter antenna manual.This manual also has the stacking information (10, 15, 20 meter LongJohn)http://www.hy-gain.com/pdffiles/LJ-105CA.pdfThe LJ-105CA is a current production Hy-Gain / MFJ antenna.http://www.hy-gain.com/Product.php?productid=LJ-105CA
USE the measurements in Hy-Gain manual, rotate to horizontal polarization,
should be a nice antenna for 10-meters.
BTW, double-check the assembly hardware.
In the 1960s and 1970s many antenna mfg. did not use stainless steel assembly hardware.
Assemble with SS hardware and anti-corrosion product it will last for years.