[Brion Toss]

Hello,
I'm with Jason on when and how much to set up the runners, but I really like a single, continuous line of sufficient strength and inelasticity; we use T-900, spliced to a Regatta Braid tail, and we'd be happy to make you up a set, as well as specifying deck blocks. This setup assumes you'll have a winch available on the weather side, which is just about always the case. The trick is getting a fair lead to the winch.
How old is your Valiant? In the bad old days, they had aft-led intermediates, before Bob Perry realized they were silly. If you have leftover intermediate chainplates, consider them stowage spots for the runners.
Tune the forestay so that it puts a bit of bend in the stick. That way you won't invert the stick when you crank on the runners.
Fair leads,
Brion Toss