My DIY plumbing has been strictly PVC except for adding a valve and hookup for an outdoor natural gas grill. I have a plastic flex furnace supply line that whistles so loudly you can hear it outside, it's a real pain in the ear. I think it's because it has a sharp bend in it right where it connects to the supply, but has to with the current plumbing - the supply is pointing straight into the a/c drain line. Long story short, I want to put an elbow in so the flex line can connect vertically to the supply instead of awkwardly between other parts of the HVAC and am hoping the whistling will go away. Without redoing a lot of the plumbing, I still have limited space, so I want to go from the brass valve to the flex line with one connection. All I could find was a 1/2 flare to 3/8 flare 90º. Can I use that flare fitting without any issues? I'm assuming I'll need to dope/tape the 1/2 side, but I thought I'd ask about potential problems since the flare on that side is just going to be sticking dumbly into the threaded pipe. Alternatively if I'm off base on the whistling and there's a better solution, I'm all ears.