The following way to "tame" spin sheet worked quite well for me:
We put a small piece (about 20cm) of velcro tape (the "hook" side of the velcro) on the front beam. If you use a somewhat soft spin sheet (such as FSE racing sheet) then it will stick to the velcro very well. Supposed that the velcro is in the right position (or long enough), the sheet will just fall on the velcro and stick to it after lowering the spinnaker.

Ceitzi