Since no one answered, I had to look it up myself. A 419, with clamp and Seachanger module, weighs 28.3 lbs, or 12.8 Kg. Still less than two standard S4s on a 24" Dbl-Tee sidearm.
Gafftaper, I said 1/2" threaded rod, not pipe, and I can buy steel 1/2"-13 x12" threaded rod for about $3, plus nuts & washers. Your solution is more expensive, but less likely to be purloined for other purposes, I'll concede on that. Did you order long, or additional, safety cables, to go with your taildowns?
Yeah I'm just planing to use extra safeties for now. If I find I use them a lot I'll use my shiny new swaging took kit to make some extra long ones myself. I'm not sure how much I'll actually use them yet. It seems like a good idea for the black box now but It's hard to know until I get in the space and actually try them.