The reason for changing the guts of the brush is not because of the needle diameter, but the trigger feel and action. The Micron uses a very different chucking guide, chuck, and spring retainer than the 100sb, and allows for a feel not obtainable with the 100sb through simple adjustments... Buying a 200b Irregular B grade as well as the 100sb is cheaper than the sum of the minimum parts listed above. The trigger action of the 200b is far superior to the 100 series... You will never add an Iwata part to an Olympos brush and have something that works better than it did before. Nothing against Iwata, I love their brushes, but they are designed to work where they are put. All that being said, through this effort, you will create a brush that works nice, and smooth. Should have good atomization, nice paint lay down, and work at relatively low PSI (Like I said - I have the 200b, and it is a very nice, little brush - with all this conversion stuff, all you are talking about doing is piecing together what would be a 200sb, if Olympos offered it). This is still not a Micron, in my opinion.