You don't really need to do the switch from PAL (PAL is not just the UK, by the way) to Japanese setup on the fly, you can do it rather from the North American setup, since the game accepts that region fine and doesn't display any lock-out message with it. In fact, it is better to do it that way, since the game balances the music speed according to what frequency is used at boot, and if you do a 50hz to 60hz switching process with the game already booted up, then you'll get speeded up music as a result. What? Do you really think this is an Amiga game source code that was converted to the Mega Drive by means of this building process? THIS source code is from a CANCELLED Mega Drive conversion done by the developer itself, since this game was stated to be officially released by Ocean on the Mega Drive. That means, this is Mega Drive code that was programmed at NEON Studios back in the day. If this source code had to be rebuilt by using an Amiga environment and programms, it's simply because the game conversion was developed that way, through an Amiga, and not because it's Amiga source code that was "magically" converted into Mega Drive source code by these means. There's no magic here, it's all the standard procedure. The Amiga Mr. Nutz 2/Hoppin' Mad game is a game in its own, and this leaked code that was rebuilt into this beta is a separate Mega Drive conversion effort that was worked afterwards by the NEON company like all conversions are done. If you really want Amiga games being converted to the Mega Drive without having any source code or pre-done conversion assets or anything, then that's an entirely different and way more complicated story. And let's not talk about doing the same with "Sega-16 arcade" (I suppose you mean System-16?) games.