My bet is if you ran a Tufo S-3 lite either 18 or 19 mm you'd get in the draft box.

Having said that, I use Pro S-3 21 mm for my spares. If I really wanted to get that tubular in there I'd try a 18/19 mm but in IMWI roads that might not be the best. I tried the putting the pitstop in the draft box but I did have issues removing the lid easily and thought in a race situation that might not be ideal. So I went with this setup.

I don't run Tufos on my bike but I think they make excellent spares because I can jam them up into the seat and not worry about rubbing/sidewall damage and they fold better then Vittoria which I use on my bike. I think you can do better than taping your pitstop to the top of your draft box.

This is my setup for IMWI last week and it worked nicely and everything is tucked away, you can barely see the pitstop from the front section. Actually there isn't anything special about this versus non speed concept setups. In addition, I went with a water bottle between the bars and my nutrition on the downtube holder so I didn't need bottles off the back. Also note, some of the tire is run up to the nose so the rest of it fits securely between the rails - you'd want to run what is needed based on your rails (at the rail contact points, the tire has electrical tape just in case it does rub). If I flatted, I could remove the pitstop and still have the tire secured in the event pitstop worked (tire secured to seat, pitstop secured to tire).

This setup did not move one bit during the race.