I am trying to choose between these two options. Any input ? And advantages of each setup would be appreciated.

1 sub obviously won't need as big of a box, but the cone area advantage of the BLs cannot be beat. I'm sure you are going for loudness (both will sound good), and I'm expecting you to be putting in rated power. 2 BLs.

Goals etc?

I'm looking for it to pound really hard but still have some pretty good sq. Yes rated power will be used. It's going into a civic coupe

The single BTL would be cheaper, and in a CIvic it must be enough !

2 BL's can be louder though !

Would two bls be able to hair trick with 1200 watts each and the 4" vc option

Would two bls be able to hair trick with 1200 watts each and the 4" vc option

no

Would two bls be able to hair trick with 1200 watts each and the 4" vc option

Kind of a lame way of making your decision IMO. But my single 12" BTL does decent hair tricks on 2000-2400 watts

Honestly with that power, i would just get maybe a BL 15 or 2 SSDs maybe. But from your very vague question, for me it would be 2 BL's because the cone area is doubled and thus be louder and you have more coils to dissipate heat and be more efficient.

I wasn't making my decision based on the hair trick that was simply a question. And does anyone know what the power handling goes up to with the 4" vc on the bls. I head 500 watts but I wasn't sure.

1500 watts

Ok so I decided on the two bls. I have the blue prints for the single twelve box. Any idea how to adapt that for two or the recomended cu. Ft. ?

for 2 BLs id go for 4.0 cubic foot and low tuned like 30-32hz.

If you have the room, and your goal is spl, go for a slightly larger box maybe 5 cubes with a nice size port.

So I appreciate all thE help and one more question. Is there any way of doing these two subs with rated power and not have to get a high output alt. I was tryin to stay away from doing that but if it's the only way then I guess I have no choice.

I dont know if it is recommended but there are many people who have more than one battery on a stock alt so you may want to explore that option.