it is indeed to reduce crankcase pressure, its pretty normal do to.
the bandit 400 alreaddy has the holes in the crankcase to make it possible. with these holes the b4 standard has a very small opening between the cilinder, in this case a bit bigger will be good.
you can see them on this picture between the 1st and 2nd cilinder and between the 3rd and 4th cilinder
in the kicxstart (dutch motorcycly magazine) there is an article about someone who uses the crankcase pressure of a 4-stroke cilinder to supercharge a 2-stroke cilinder.
v-twin with a 4-stroke and a 2-stroke cilinder