I use a micrometer attached with a clamp, and made my weight with lead ingots, and found the charts on line. Set it up to be not collapsible but it can easily converted to breakdown mode. I think I am going to make an arm the will support fletched arrows, too! I can send you a base and upright (walnut)' you just have to make and set the yardarm, and mount the pegs.
Hawkdancer