Joe, The plus to using the aquarium tubing is that it doesn't cost very much. You can make a longer coupler, that will work too.
Also, I notice on my Singer 224 that I'm using lots right now that I did have to shorten the tubing since it kept slipping off. With the temperature up in the 90s ( I have house temp set at 80), I notice the tubing stretching. I have tubing on the Two Spools, but I had already shortened months ago when the temperature was cooler.
Let me know if with lots of usage and warm temps if your tubing stretches.