Hey Tobylou....here's a solution for the highway.....get a pocket trumpet!! LOL. I've had adult students that have done that and it's more fun for them than a mouthpiece, heh. But again.....I still reiterate that the mouthpiece alone is way different than on the horn cuz the air column is different. "Mouthpiece tube is too short" to quote Charlie Davis. Need the rest of the venturi(leadpipe) at least to be playing on the same "resistance" you'd get on the horn,etc. It's about tongue and air coordination here which again is two different things mouthpiece alone vs mouthpiece in horn. THIS then coinsides with the fact of "how" an air column hits the lip cells in your lips. Playing will be more consistent then if you keep stuff the same and playing on the same air column shaped by the same resistance. Mouthpiece alone again is different air column and resistance than when in the horn. They "fight" each other and during the battle one's tongue/air coordination for playing the trumpet gets thrown out of whack.