an on-the-roof version? no muddy wheels in the car.. and available all the time..?
In other news, your colour scheme reminds me of a 70s jumper.
I lost the campaign for that, roof is filled with kayak carrying capability... although originally I didn't want roof anyway because 95% of people I know with roof mounts have had accidents... now its about 97%.
There is an adapter you can get, which goes where the top tube normally mounts then grips the down tube and the seat post. Sounds dodgy.
Nic has the identical set-up and says she "rests it on top". I'm waiting for a photo.