Personally, I would NOT go with option 2. I would go with a modified version of option 3. Use a length of 2-56 or 4-40 rod (whichever fits your application) that is threaded on the end. Cut it long enough to insert into the plastic tube beyond the unsupported area and simply thread it into the tube from the backside of the threads...I hope this makes sense! This way, you could even go with option 1 as long as the metal rod inside the tube extends beyond where the yellow enters the red tube..

-Johnny-