I've tried just about everything too! The replacement "long" tube is horribly designed.
I actually cut off the screen-end from the original brass tube.
Then cut off the small end of the plastic replacement, install in my 5C collet chuck (lathe) and drill the I.D. to a press fit over the original brass tube.
One of these days, I'm going to sit down and design a better way to accomplish this upgrade...and I'll probably tap the hole in the bottom of the carb.