...I asked Quest for their opinion on how well shorter sections would flex for shorter sections for the arch, but they didn't respond. To be fair, if they did advise and a pole did happen to crack, they could have comebacks. So you're on your own. (the Syclone set from Tentpole Tech is 7 section with more manageable pole lengths with a prebent alu centre section) - when I get around to getting another set I'll have a go at shortening the 3.9 poles just out of interest. I reckon a 7 pole set would work now having seen how flexible the 18" sections are, but you then have the extra insert weight, so, for now I'm sticking with the 18" - and just stay mindful of the exposed ends... A 7 section 3.9 set should come in at under 100gms though.
Drapers elastic used for shock cord - think it's around 1.5mm.