I started to race bmx when i was about 6 so I was using SPDs back then.
luckily I knew the benefits so the transitions was worth it x100.

and although I have 105 on my road bike, I agree with recessed cleats for the kilo which is why I made my Vans into SPD.
-buy some ugly cheap shoes off nashbar.
-destroy them and remove the plastic sole
-hot glue the whole thing into the shoe of your choice (make sure you measured and cut the hole already in the bottom of the shoe)
-attach cleat

-enjoy walking around like a cool guy.