Cable tension does not matter all that much with friction shifters. If the cable is too tight, then you will not be able to shift into the smallest/smaller cogs. If the cable is too loose, then you will not be able to shift into the largest/larger cogs. The no tension limit screw is set without the cable being attached.

Having a slightly slack cable for the smallest cog is no great deal with a friction shifter. The chances are that you will shift one cog at a time. You will get the sense of how much to move the lever to make a shift. It's most unlikely that you will move the lever more than is necessary to make a shift. Also, if the cable is slack and you are adding tension in the shift, you will be able to feel when tension begins. You will go quickly through the no-tension zone.

I don't have stops on my friction levers; they did not fit over the spigot. I can put all the slack I want on the cables. It's never caused me to miss a shift.