Well then, I suppose that the brightest idea would be to test the game on a flash cart before going out and spending money on a reproduction cart, although in the long run I'm not really sure if that'd be more economical. I should probably research a little more to find out if Metroid II DX has been tested on real Gameboy hardware or not.

BTW Pootle, thanks for the offer. I'll definitely keep you in mind if / when I decide I'm ready to get a cartridge made up.