^^I do downshift, but only about 1 course or so a year, and I usually end up being faster by just finding more speed through the corner to stay close enough to the powerband. It'd be a very odd course that's fast enough to get into 2nd, so slow through the corner that it requires 1st, and so fast out that staying in 2nd would totally screw you.
If you're approaching the corner in 2nd, you're going fast enough to get any sort of rotation that you could want, which means that you should be able to get through the corner with enough momentum to stay at least pretty close to your power band. Not to mention that even if you do nail the shift, about the fastest you can do it and get back on the power is half a second. 5 tenths is pretty significant in the AutoX world, and just as often as not where I have tried it I end up hurrying it, missing the shift, and screwing the whole run.
With only 4-6 runs for an average race, it's something to try at the end if you simply can't find any way to get through that section fast enough, but on a whole it'll penalise you far more often.
Don't waste another minute waiting on parts, or anything else. Just get out there and start racing! You will suck at first, and you will be slower than many other cars, but the only thing you will regret is not starting earlier...