Playing Genesis games on a Japanese Mega Drive?

Recently I bought a copy of Jungle Strike even though I have no Genesis (I was about to use my RetroN, but turns out that I'm missing the AV cables). I'm not sure if I want to get a Japanese Mega Drive or not, because even though I'm pretty sure Genesis games will fit into it I'm not sure if they'll play. Have you had any experience with this?

Also, another question. If it cannot play Genesis games is it legal for me to cut the plastic on a Genesis console to allow Mega Drive games some space?

@LeonChameleon: One thing you can do to circumvent the physical region locks on old cartridge games would be to use a Game Genie or similar device, those act as a bypass since the system does not actually have any programmatic region locks between the two NTSC consoles. Just put the Game Genie in the Genesis and slap the MD game on top and it'll play just fine.

There are also adapters for PAL to NTSC and vice versa as well, though it doesn't sound like you would need one. Another popular adapter is the Honeybee, there's one for NES(for Famicom games) and another for Genesis(for MD games).

I'm also quite sure the Japanese had devices similar to a Game Genie which you could use to play PAL and NTSC-US games on an NTSC-J MegaDrive.

Going from MD to Genesis, if you're using the NTSC-J version of the games, you can either use a Game Genie like suicidesnOwman said, or cut the plastic, which will work as long as the game doesn't require a code to get around region locking like Alien Soldier.

I don't have experience going the other way, but I'm assuming they'll play perfectly fine if the cartridges fit.

@Renegade_Fury: I think I would just mod the game genie cart instead of the console, it's just a bypass cart. I bet if he shaved about 1-2cm off the outer edge of a US Game Genie it would fit in a Japanese MD.

Sure, that could work too, though if what the TC is saying is true, that might not even be needed if a Genesis cartridge can fit inside a Mega Drive without doing any physical modifications. I only have MD games and haven't seen a system up close, so I don't know if the size of the cartridge slot is wide enough, but in any case, there are a lot of easy ways to get around region locking for the Genesis/MD.