Don't use neoprene. Do a search and you'll see me and others reporting problems. It just deterorates and plugs up your carb screen. Tygon is fine if you leave some fuel in the tank to keep it soft. I'm going to try Viton for the clunk next time I re-plumb. It stays flexible. I'm using the Walbro felt clunk and a Final filter in line with the carb. This is a system that Jody said works for him and it's working awesome on my DL-50 and DLE-55. I didn't used to use a filter because my gas fill can has two but after all the plugged screen problems I decided to try the Final filter. Works great. It's not serviceable so it can't leak air.