When to play Bf5 in the Slav?

I was considering the Slav with Bf5 played in this position, but I think it might be premature. Can someone with more experience with this position confirm this?

What will you do after cxd5?

Recapture with ...cxd5

5.cxd5 cxd5 6.Qb3 forces 6...Bc8.

Why wouldn't 6...Qb6 work? Is it because it weakens black's queenside pawn structure after 7. Qxb6 axb6? Because I don't think that weakness is great enough to necessitate undeveloping the bishop.

Actually, with more thought, I think I like the Czech variation. It seems much better than what I was thinking.

5.cd cd 6.Qb3 Qb6 7.Nd5 Nd5 8.Qd5 e6

5. dxc4 a4 6. Bf5

I was checking out some lines when I came across this one in one of Capablanca's games. This is the Czech variation I mentioned earlier. I think this is probably the best line for me.