Nacra 6.0 spinnaker going upwards?

Hi all,

We've been sailing a nacra 6.0 with spinnaker lately and have been using the single halyard - tramp bag system, not the original. The problem we've encountered is that the spinnaker gets pulled upwards towards the mastblock instead of staying at the end of the spi pole.
Does anyone know why this happens? and of course what to do about it...
I know we might place the block in the masthead lower to prevent this problem, but then the distance between the top-block and spi pole end would have to be exactly the length of the luff, and if it would be just a bit more, the spi would keep going up.
Is there something we're missing here?

thanks

Sander

(nacra 6.0 no 139)

Sander,

Ideally, you want the luff length to match the distance between the end of the pole and the hoist on the mast. However, you can simply place a plastic ball above a knot on the halyard to control the hoist height. Adjust it until you can grab your un-winded luff with a fist and turn your fist from vertical to horizontal (90 degrees) and make it tight.