We've done some practice with out streamers, not trying to hit each other though, just going for "phantom streamers". Intentional contact just causes too much damage to airframes, too much shop time.

We do use forestry tape and no wing stickum for practice though. The streamers usually just slide off the wings, but you can still hear and see the "drapes" and the streamers last a lot longer. Props still cut them, of course.

And yes, the AMA now specifically doesn't allow intentional contact for glow-powered planes. Electric Zagi-style and slope full contact combat are popular though.