your linen thread sizes are referenced by (cord ) 6 being the heavier 3 being the lighter. 5 and 6 cord for harness and saddler, 3and 4 cord for purses wallets ect. As far as needles go depends on the manufacturer, I believe Osborne 000 are the heaviest, where as 0 and 1 are smaller. John James needles, I use 004 which is there smallest harness needle and I use 5 and 6 cord with this needle, I Like the smaller needle as I can pull thru the awl holes easier. I taper and wax the thread and I am able to thread the eye, I do not back weave thread thru it self as most do. You may want to try this with your number 2 john james. The 207 is a thread size reference for machine thread poly, nylon,ect. Machine threads go from the smallest 46,69 99,138,207,277,346,415, the largest. 207 is an med size used for belts and light weight tack. you can sew by hand with if you like but it is not as nice as linen.