Faddraio
I am not sure what you are doing, but the time signature may not really matter, because 12/8 and 4/4 are pretty interchangeable. The time signature 12/8 is 4/4 with triplets on each beat, and is frequently used for what we think of as DooWop. In fact even some of the sheet music for those 12/8 feel doowop songs are written in 4/4 anyway. They just have 4 beats with triplets on each beat in each bar. It doesn't really matter.
And on Yamaha arrangers the on-board styles for 6/8, 2/4 and 12/8 usually all appear as 4/4 time signature. The 12/8 or 6/8 feel is more usually in the style title, not the time signature.
The time signature is not that important on styles because the feel of the style is what matters for the song you are playing, and you already have that ( or create that) in the style. I could go on a bit about why time signatures really are important for reading and interpreting sheet music, but will skip that except to say that in styles it is generally unimportant and the only issue is the length of the bar, and maybe how that affects bar length fills. But that really only applies to 6/8 versus 4/4 -- with 12/8 its an irrelevance. The bar is the same length.
Mike