Switched from standard DBPro joystick input commands to using "multijoy" plugin, which is great! No longer have slowdown with multiple joypads. Game now configured to use keyboard or joypad (no support for joypad in menus yet)
P1:
WASD. left ctrl (A=fire, D=bomb)
P2:
Arrows, right ctrl (up arrow=fire, down arrow=bomb)
joypads:
left and right on d-pad (must enable digital mode)
1/2 or A/B buttons for fire and bomb
right trigger = thrust