It probably isn't necessary to get flats, but if you want to try them go for it. The biggest tool for that sub 40 10k is to increase your mileage. 35 mpw is pretty low when you're trying to push yourself in a 10k. But you have 6 months, so there's plenty of time to build up. Most important thing is to stay healthy. Don't go from 35 miles this week, to 75 next week. Gradually build your mileage up, I'd recommend up to around 60-70. Again, don't do it all at once, do whatever is necessary to stay healthy. Flats won't do anything magical, it's all about you're training. I'm not a true 10k guy, but my PR is 31:19, and if I were to run a road 10k, I'd do it in trainers. But that's just me. Do some more research on flats vs trainers, and keep training hard. Best of luck to you!