Tkh1975

I’ve got a Juki DNU 1541 industrial machine. I plan on sewing a leather strap. It’s about a 5oz strap. What thread should I use and what size needle? My machine takes a 135x17 needle. I have a Groz Beckert size 20 needle. It’s says RG on it. I don’t know my industrial needle as you can tell. It’s that the type of tip? Any help will be greatly appreciated!