TromboneChat

Having played dual bore (525-547...old Conn 14H) for many years. I got a very good stencil 88H. A HUGE lesson in air management. I realize it will take a minute for one m'pce to find assigned parking.
Down to a Tale of 2 Wicks..4BL and 5BL. Day by day I can play longer phrases on the 4BL and trigger notes speak freely. It seems counter intuitive that the 4BL upper register is marginally easier on the 4 over the 5. I would rest easier with the 5BL if I didn't have to make an appointment (sometimes/contextual) for trigger notes.
Question that I can't figure is how does the 5ABL compare if at all between these two? Looking for some direction without buying yet another m'pce..

The 5ABL has the same rim and (deeper than the 5BL) cup as the 5AL, but a tighter backbore than the 5AL. It is a compromise between the 5Al and BL, although I always wished Wick made a cup depth in between the two: the 5AL sounds great, but it is very deep and a lot of work sometimes. The 5ABL is a little easier and takes a little less air but lacks some of the fullness of the 5AL and the tighter backbore only goes so far in aiding the high register.
It’s not necessarily counterintuitive that the 4 might give you a better high register. Depending on your face, placement, and embrochure, a bigger mouthpiece rim may actually work better for you. Go with whatever actually works best, not what you think should work best.

If your issue is air management and finishing phrases, you may not need a different mouthpiece, but instead you might need to use your tongue to help manage your airflow better.

With small equipment we can get into a trap of trying to play "huge" on it by being really "open" in our mouth, throat, aperture, etc. With an 88H or the like, you don't need to do that. It can work against you. Think of playing focused and compact instead.