Just to put a closing statement on this thread: in the end, I went in with United Gold, and I ended up paying nothing -- even though they DID size our luggage in both LIS and TLV and find it to be too large. In LIS they sized at the gate and gate-checked the luggage (which still went to the carousel.) In TLV they flagged our rollerboards at the ticket desk, and checked them through to our final destination. But in none of these cases were we charged anything, despite having four suitcases when Gold status only gives you one free one. So I guess I still don't really understand what their rules are!