larger needle- a 16 - 18 is good....visit Superior Threads web site- they have free charts you can print off that tell you about all the different threads, the different needles, what needles are best with what threads and what projects each is best for. I pretty much never use cotton thread with the long arm- they go fast- the cotton threads break- I do use cotton if quilting with my domestic machine- but they also create ALOT of lint. for long arm quilting I choose a good polyester, Aurafil or silk...depending on the project and what is the best choice. also, I generally quilt with a 50-60 wt thread...some people choose a heavier thread- 30-40 wt...it's really a personal choice- project dependent- and every machine has it's own personality, likes & dislikes- a thread I have great luck with your machine may hate & the one you love my machine may refuse to work with...