Don't do it trumpetguy, keep the horn. I too have the 4-valve Getzen, and it sings with the Getzen 3C mouthpiece. I have testimonial by a TM member who heard this horn live while playing with my quintet, that this horn was the best flugelhorn sound he ever heard.
OK, the Getzen Eterna has a 0.460 bore. All you need to do is fill it with air then blow lightly...just ever so slightly pushing the air through. You do not have to overblow to give this horn sound. That is what is sooo cool about the Getzen Eternal sound. Very little force, and just finessing the air flow, it is so thick and rich when played this way. Keep the horn, because if you sell it to Coolerdave, cooler will then truly be cooler than you.