I've been working on this too. I cant quite see how sticking another tip in it is practical. I tried to make a stencil tip at work (its a metal shop and I can fabricate just about any thing there). The first one worked, but after that the paint just splashed and dripped everywhere after the first 30 seconds of trying to paint with it. I think the real answer is can control, technique and creativity. Fan tips are sold online and it serves it's purpose. I like the new colors they are coming out with and they are at least half way decent for a fill in. but for an outline you have to either turn the can as you go or adjust the nozzle to the appropriate line or thickness desired. creativity is the key weather you are trying to adjust to the new nozzle or trying to adjust the spray to fit your preference. Skinny, fat, whatever you want you can do. the changing world requires us to adapt. and good design never goes out of style. try to design a style that flows and where the lines go from thick to thin as if you were painting with a fan tip. you can use a chisel tip marker to experiment with different letter structure that are conducive to the lines going from thick to thin. any way keep working on it let me know if you have any more ideas.