I have an idea how to use +4 frames advantage of B1.
After B1 you should not try 21 ice ball , because 2 will have 11 frames of advantage, then any stroke of less than 11 frames can hit it.
Using 1 will have +5 frames of advantage. No poke can beat that.
So if you are sure that your opponent will try to fight back, 11 ice ball is thrown.
I believe that the best option would be 111 because it is in lock 0 and +8 hit.
With +8 frames of advantage you could do mixup with 34, 334 or 33 ice ball mb. Or could still press with
211 + 2. Of course pokes of less than 7 frames can win this string but his opponent had to do it at the right time.
If your opponent defend 111 try to dash d1, d1, 211 + 2 to continue to press it.
I do not know if my calculations (based on the data frame) are right and not everything said is 100% safe but worth trying this