I have a cutter rig with the stays'l at about 3/4 the mast height. I think I see what you mean about adding security. On my deck-stepped mast I have double lowers, nicely spread out on either side of the upper. The forestay and the inner forestay and the double lowers all work to stabilize the rig nicely... but there is only one back stay... so the runners would add stability to the rig at the inner forestay level, OK I can see that.

BTW I have a tiller, which on my small boat gives me lots of cockpit space, and means that I tend to steer while sitting close to the deckhouse, well shielded by the wide coamings, with my eyes barely above the deckhouse. I like that a lot, it's pretty darn dry even in a rough seaway. The design of the deck house, and sidedecks and coaming tend to shed any breaking waves down the sides and out through the side drains. (not really a scupper)

I couldn't really see the runners being used to tweak the rig for racing... so I was wondering when they might be used... seems like stability is the order of the day. Probably use them when running with a kite too... have not done that yet on this boat.

Thanks.