Re: yamaha soprano question
Making the resonators larger is the best chance you have at making a noticeable result. Don't fuss over plastic vs. metal - flat vs. domed, etc.
Having said that, with all the expense that goes into outfitting a horn with new pads and resos, I think you would be disappointed in the outcome as the difference is rather subtle. If it's volume of sound you are after, going with a larger tip opening mouthpiece is probably the most direct route.