Actually, it's the CHR-ROM that's doubled in size. The PRG-ROM is the same. (total size 3mbit to 4mbit)
Yeah, Nintendo added some copy-protection to the game. It was only hacked because Nesticle, the popular emulator at the time it was dumped, was inaccurate enough that it broke the unhacked game.
Of course, if you still want to work on it, that's okay. But Tomato is working on the GBA port now, and it seems like a duplicate effort to retranslate the whole script from scratch (as I hear Mr. Itoi was insistent on leaving the content mostly unchanged, aside from a few enhancements made for the canceled NES version). Perhaps you may want to ask about sharing?
(more specifically, Tomato plans to do a real serious effort on Mother 1. As for Mother 2, he plans to "CyberGoth" it (for the less longtime sceners, it means he does a simple translation of the menus and items, just enough to make it playable to those who already know their way around EB). He says M1+2 is practically 2 self-contained games in one, and he wants to leave Mother 2 to someone with the time and effort to tackle it alone.)