mec funnel tube options

ive seen some recent discussion and wtb ads for mec funnel tubes.
I picked up an old 600 in 20 gauge, my 3rd mec in 20 ga, anyway this one is missing the funnel tube and I've been thinking about how to make one.
fortunately ive got a pretty good stash of copper tube in wide variety of sizes. and I had this idea of using a pipe flaring tool, starting with the conventional type flare tool then going to a larger cone I happen to have for a hydraulic tube flaring machine . once I locate all the pieces and parts to do this and give it a try I will try to post some pictures.