Embouchure or Mouthpiece problem?

[Ramardpenovi]

I ve been having an issue since april with my small bore yamaha 351 trombone:

I have 4 mouthpieces: Bach 12C, Bach 7C and a Warburton 10M 3T (Kind of a shallow 6.5A, V Shaped and a more open thorat) Yamaha 48
Thing is that i'm having multiple problems mostly related to Endurance, but this problems vary in intensity depending on the mouthpiece, whenever i play above 5th partial for a sustained amount of time my lips collapse, and everytime i put a mouthpiece on my face feels like im mashing my lips to make a sound is like i can feel the metal edge thorugh my lips. This is more notorious on the 7C, which leaves a swollen sharp mark on my lips after an hour. (With the other two not so much)
The 12C feels much more efortless to play overall, but fast playing is impossible, also high range with that one is a waste (compared with the other two, i can't get to play a C5).
I like the sound of the 7C, its jazzy and balanced, but again there is something off with the rim that kills my endurance, but i feel like its the best suited mouthpiece for my playing. As everything else does not feel that bad.
The Warburton rim feels better than the 7C but after 2 hours of playing i get a similar feeling, this one feels like i m blowing a bass trombone compared with the other two, and it dosent have that spark on the high range, also the sound feels unfocused. But articulations feel better with this one. Also.i think that its way too big for lead and jazz playing. I play 1st trombone on a local big band, but even for solo playing i think its not suited for jazz (which is all that i play)

Maybe its a embouchure issue but when i start playing i initally sound great, the problem is after i played for an hour or two.

Thanks

[Doug Elliott]

I'd have to see you play... is there anything on YouTube?
The 7C has a horrible rim shape.