Steve, I'm surprised the duty cycle is that low. Maybe some part of your test setup is not reponding fast enough. It doesn't matter much once you know the bit sequence, you can try the Pronto with the observed duty cycle and try it again with a higher duty cycle.

Do you get a good enough view to write down the whole bit sequence? Do you have the patience?!

You should download my Makehex program from the utilities area here. It should be easy to write an IRP file that generates a code with the same timing as the Pace (If you don't know how, ask and I will post one). Even before you find the correct bit sequence, it would be a good idea to use your storage scope to look at what the Pronto actually sends when you program it to match the Pace timing.