What Abus lock are you using? I looked at my Bordo Granit X-Plus 6500 and I see no way to tuck it there. I carry mine attached over the hump, but I would not mind moving it out of there to allow for a handle at the location.
Yes other (Smaller?).. Abus Bordos fit behind the seat tube.. , low. flip the rear latch lever over.. to make space,,