Hello Y-O-Y. I have thin lips, on the smaller scale end of the Stork Mouthpiece Lip sizes to Rims sizes Charts. You should check that out. When I down sized back to a Bach 7C to Bach 10 1/2C rim size,playing and range improved. There are are other factors to consider also. You may need a mouthpiece with more bite or higher Alpha angle. I can not say all thin lip people do,but I seem to like pieces with more bite or grip. I can play a Del Staiger Cornet m.p. with that sharp inner rim. Cookie cutters m.p.'s do not bother my lips. A good lead m.p. that may work for you, could be the Conn #5 Precision Trumpet m.p. Has a small rim size, Med. shallow cup, good rim bite, and large back bore. One in very good condition may be hard to find. I am a come back player from way back. Playing up to A on top of Staff is just fine for me. High as I need to go. Plenty of music can be played from that A and below. I have music scale charts that state, that the A above staff to A below staff is the best sounding range of a Trumpet/Cornet. Another thing to consider is, all of us are not cut out to be Lead Trumpet players. Someone has to handle the Harmony. I enjoy playing the Harmony with the lead Trumpet player in my Church. All the pressure is on him,I can miss a note or two,no biggie,just come back in on que. If he misses or cracks notes,everybody hears it. Another thing is the bore of Trumpets,high note players prefer the Xtr large bore horns. But their are some players like myself,who want to feel the resistance,and can control the higher and lower range better. Anything past a .468 bore for me is hard work in practice. So to all the thin lip guys out there,who can not play that High screaming stuff. Forget about it, there is plenty of second and third parts that need to be played. Y-O-Y find you a good lead player,learn his quirks,let him lead,and enjoy the harmony. Your thin lip problem will be solved. Look at the great Trumpet player Vacchiano. He did not have big thick lips. There are just as many thin lip lead players as there are thick lip lead players. Good luck,from a thin lip, third seat trumpet/Cornet player and loving it. P.S. hope to soon try out a Flugel. Yeaah Baby.