Originally Posted by
bicycleflyer
...The 400L does come standard with two styles of mounts. One will mount the light horizontal and the other will mount it vertical. So when you ask for those additional mounts be sure to specify....
I don't think that matters - the part of the mount the determines horizontal or vertical is the part that's screwed to the light, while the part that's attached to the bike is the same for both.
...I'm pretty sure?
Just call Dinotte, tell them what you want to do, and they'll be able to include the correct extra mounts that you'll need. :-)