Been using a Boss for years, bought a nice used 1541, been running round point 135x17, I found some 135x16, 140 size 22...is this the biggest? What would be the biggest needle I can run in this machine? I have searched here, looked at the manual, and googled, but I guess not understanding what all the numbers on the needles mean is a hinderance... I would like to run a 138 nylon thread, and should I run the same size in the bobbin? Or a size smaller?