The key I initially bought from the locksmith was also long like the one that maxtog has.
I went back to the locksmith and he found a shorter blank to use. Works perfectly.
I did the same as kzz1king, but used Radio knobs instead of oil caps.
I suspect we both built them so that they barely stick out of the top of the bags.
Not noticeable at all. I tell folks mine are knobs to adjust the stereo.
{Surprisingly, most believe me).
I use a leather key case that I put my Fob, lock keys, spare trunk keys, and keys for the gas tank in.
Very handy..
NOTE: I'm always concerned I'll loose my FOB, so In the key case I have a dog tag with a note saying "If found, call ###-#### for $100 reward".
Ride safe, Ted