Unusually we have a staysail (trinquete) on our Super Maramu.
We had a staysail on our previous 12m IOR yacht also.
You use the running backstays ALWAYS when using the staysail, because it supports the mast.
Otherwise the only support is at the top of the mast and the tension on the staysail luff will cause the mast to pump, which will destroy the mast in  big winds.
So the deal is when you sheet the staysail on the port, side for example, the running backstay on the starboard side is wound on the starboard winch...tight.
When you tack, you swap sides, staysail sheet on starboard winch, port side runner on port winch...  
Generally going upwind in strong breeze is when we use the staysail, the genoa is too baggy when reefed, it's not possible to maintain a good angle to the wind.

So ALWAYS use the runners when going up wind with the staysail.

Cheers
Alan
Elyse SM437