Being a bit annoyed by the relatively poor shoulder check visibility to the right with the top up, I have bought and applied a small convex mirror which is now attached to the passenger side outboard mirror. You see alot of trucks and vans with this.
I tell you that it makes a world of difference and allows those lane changes to the right to be done with 100% confidence. I highly recommend it. Note that after a bit of experimentation I found the best position was on the mirror near the left side of the mirror - otherwise you get too much of the mirror cover in the fielfd of view. A $2 accessory that is well worth it.