You know, I've been following this thread and reading everyone's suggestions with great interest, but have come to the conclusion that the only way to keep them off those rafters is to slap some chicken wire all across the entire inside (like a false ceiling). You could use those plastic zip ties which will make it easier to put up. That would solve the problem of them getting up there. A cheap and easy 'fix'. Then build yourself some roosts (if you haven't already). Oh, I'm sure they'll raise holy heck when they find they can't get up there, but they'll calm down...just thinking and JMHO.