I have difficulty cleanly attacking lower register notes with my f attachment .547 bore trombone using a 1&1/2g mouthpiece. Could I expect that a larger bore bass trombone would improve these notes?
A larger bore bass trombone will let you put more air through the horn in a manner that will let you more efficiently produce low register notes. (Lots of slow air).
In my experience, this certainly helps, but will not magically solve all problems. It may even introduce a few of its own, especially if you're playing it for a long period of time, without specific bass oriented lessons.
I organized a trombone quartet to play one piece for my college senior recital, and played bass for that. It certainly made a big difference in the low register (anything lower than E) in the tone department. The articulation was better than a bass mouthpiece on my .547 bore.
However I noticed that in terms of articulation, not quality of sound, my cleanest articulation was on my normal .547 setup with my normal mouthpiece. Putting a larger mouthpiece on it simply muddied things, although made it easier, lip-wise to produce the pitch.
Your mileage of course will vary, but it might be worth borrowing a bass for a few days to see if it seems to make a difference. That would also give you a starting point as to what to look for when it comes time to buy.
A .547 bore trombone (typified by the Conn 88H) is classed as a large-bore tenor. A 1 1/2G mouthpiece is a bass trombone mouthpiece. My advice would be to not go larger than a 4G on this instrument. This will match the instrument and allow it to do what it does well. You should have no difficulty in playing down to the first few pedal notes, and - more important - in making a good sound down there. Do you know about the "false" notes - low Eb, D, Db and C in 4th, 5th, 6th and 7th positions without the trigger (i.e. one position further out than expected)? They have to be "forced", but they definitely exist. You may never use them in performance, but practicing them will improve your "normal" low register enormously. To answer your actual question - you might actually find clean production HARDER with too big a mouthpiece.
You have 2 solutions depending on the "problem" you have What you describe may come from one of the two following :
Bad tongue Attack: Just Don't do tah or dah or whatever for these low notes .. Use your tongue as a valve. Close the valve put pression and open the valve !! This will probably give you a nice attack..
If your set-up is not strong enought: just try smaller bore embuchures where you control better your air stream endurance and so on ... you can play Bass Trombone with a 6-1/2 for exemple.