On 1257 were using solid braid polypropylene. It functions as the loop (soft) side of the velcro very well and can support the weight of the robot. Then we have the hook (hard) side of the velcro on the spool mechanism. It grabs every time and holds very well. And since it is clingy enough to act as the loop side there is no need to add additional velcro to the rope.
Do you guys have any video of this? It sounds awesome!