Ceitzi,

I cleat the mainsheet (also near centerline) but keep some slack and a finger through it with the hand holding my tiller (keeps it easy to find). I hand hold my spinnaker sheet. If I feel the need to let things go, I release the spinnaker first, then the mainsheet. This goes for heading up to avoid obstacles or when the hull comes up too quickly and bearing off isn't correcting the problem adequately.

I heard of a particularly good skipper sailing the Inter 17R who cleated the spinnaker sheet and "pumped" the main (not sure if he pumped the sheet or traveller) to keep the boat going fast. I haven't found this easy to do.