37 mm still knocks em down with 1 or 2 hits.
20mm will cut off big chunks if your close.
Don't get dead six, don't stay in one place too long. Keep shifting around, left to right with a shot in the middle. Then up & over, dive in for shot & go low. Then loop up & back in on his hi 6.
Mix it up, get in close so he has a harder time tracking you between guns.
As always teamwork works best. 2 go in, whoevers getting shot at jinks, other guy shoots.