I would use a Conti Sprinter with a single CO2 and chuck. Also taped an xacto knife blade to my seat post for quickly slicing the old tubular off the wheel.
It folds small enough that I would jam it under my seat.

If I got two flats I was waiting for on course support because my time goals are gone anyway.

ETA: I did get two flats in a race once. I rode the flat tubie on a disc wheel the last 8 miles. The disc was fine - just needed to slow on the downhills.

1. Put orange seal in you tires, that's your first line of defense.
2. A can of Hutchinchin Fast Air Inflator or Effetto Mariposa Caffelatex Espresso Cartridge, those are my fix a flats of choice.
3. If the above 2 do not work, cut the tub off, I use a tiny Swiss Army knife, or peel it off. Slap on your spare tub of choice. Mine is a Vittoria Corsa Triathlon 28-21, half fill with co2 to line it up, finish the canister of co2, final check for alignment. Roll. No longer than changing a clincher. Just relax and don't panic.
4. Second can of Hutchinson or Effetto in case of a second flat. Never needed.

Above is for longer than 70.3 races.

Just check your spare tub. They can dry rot especially around the valve. And don't use a tubular with latex. The CO2 loss is much much MUCH faster than butyl.

For a 70.3 I just carry 2 cans of sealant, with sealant in my tubulars. Running Vittoria Corsa Speeds with 1oz of orange seal in each.

Yeah, put the orange seal in your tires now, its primarily used for tubeless setups.

http://orangesealed.com/shop/8oz

1. Put orange seal in you tires, that's your first line of defense.
2. A can of Hutchinchin Fast Air Inflator or Effetto Mariposa Caffelatex Espresso Cartridge, those are my fix a flats of choice.
3. If the above 2 do not work, cut the tub off, I use a tiny Swiss Army knife, or peel it off. Slap on your spare tub of choice. Mine is a Vittoria Corsa Triathlon 28-21, half fill with co2 to line it up, finish the canister of co2, final check for alignment. Roll. No longer than changing a clincher. Just relax and don't panic.
4. Second can of Hutchinson or Effetto in case of a second flat. Never needed.

Above is for longer than 70.3 races.

Just check your spare tub. They can dry rot especially around the valve. And don't use a tubular with latex. The CO2 loss is much much MUCH faster than butyl.

For a 70.3 I just carry 2 cans of sealant, with sealant in my tubulars. Running Vittoria Corsa Speeds with 1oz of orange seal in each.