Std bore for B20 is 84.00mm
B16A & B18C are 81.00mm
So no, that won't work.

The talk about the notching of the pistons is because the b-series vtec head has valves 1mm bigger in diameter than the flycuts in the b20 pistons.
Aftermarket pistons don't have this issue

Use CP pistons - part number SC7117 (84.00mm), SC7118 (84.50mm) or SC7119 (85.00mm)
or if you stretch your budget use Toda 85.00mm pistons P/N: 13010-B20-000
If you go oversize, be sure to use a dummy head when bore & hone is done.
You'll need rods with these or modify the std rods (but that's kinda uneconomical)
also balance the bottom end properly (2nd order harmonics kill these engines)

hope that helps