Just an FYI...I ordered the expandable tunnel bag you are all discussing. I have a '14 RTX SE; a couple comments for those considering this bag:
1) If you put much stuff in this bag it won't fit completely in the space alotted on the tunnel, rather the end of it has to sit on TOP of the rear light (i.e. it's a bit too long even when I have it snugged all the way forward).
2) I agree with Powersports1; the Viper's seat latch definitely gets in the way. In face, after my 1st ride (only 150 miles) the seat latch has already torn a hole through my brand new bag. NOT very happy; it will be going back to the dealer.