You need to tell the game how many and which letters you load and then do mappings, which are using VRAM offsets to those letters. That wouldn't have been such a big problem though. The problem was the letters I, M and W, as they have a different size from the other letters (I=2, M and W=6, anything else 4), meaning I was pretty much fucked and had to rewrite a lot of code, when it already was working fine for any other letter.
But anyway, presenting you the Sonic 2 - Text Code Generator, a program I finally did, after months of the release of the Sonic 1 - Text Code Generator. The actual programming of this took 4 days, even though day 2 and 3 I didn't really do anything but a few artistic things.
But enough of the moaning, here's the program itself:
The usage is very simple, however, you will have to read the Setup Guide first, which contains a disassembly like file, that uses the code and is damn hard optimized to work with this program.
Oh yeah, the output of the picture above looks like this in-game (thanks to Spanner):
Download (v3.0 - 2013 Hg update)
Please report any problems, bugs, suggestions, etc. =)