I will offer another alternative solution to this achievement as I found this one to be the most useful for me personally and the track itself is not too frustrating to learn and you should be able to get this achievement with some practice.
Track: Training Run# 1
Class II (4th event of Class II)
Platinum Requirement: -0:05.511Here are some strategies and tips to help you out with this track:
1. Use the Class 2 ESA-AGR Hussar and make sure it is fully upgraded. This is the best ship to go for this achievement/trophy but other similar statistic ships will also do fine such as the Class 2 Sulha AG Racing Djinni fully upgraded.
2. Make sure for your active powerup you have: "Turbo Boost" selected and fully upgraded. This will be needed for the final corner.
3. Make sure for your active powerup you have "Magnetic Stabilizer" selected and fully upgraded. This increases grip which makes this much easier around the tight corners and significantly reduces more risk of losing speed and drifting too.
4. Make sure you go for this on your 2nd or 3rd lap. Lap 1 is not possible to do this.
5. Try not to use your turbo on some of the lengthy straight tracks. You should already be comfortably be above 800 speed without needing to use it but if in slight trouble use just a tiny amount if you need too and you should be fine.
6. When you are about to start on your 2nd or 3rd lap make sure your speed is already above 800.
7. On the first corner use some of your standard turbo to keep your speed above 800.
8. On the second corner, try not to use your turbo as this corner will not slow you down below 800. If you feel you may drop below 800 speed, use just a tiny amount of turbo and you should be fine.
9. On the section where there's 2 corners, turn left and quickly right. It is possible to do it without needing to use turbo but i recommend you use a small amount just to be on the safe side.
10. On the final and heavy turn which is the trickiest part and can make and break whether you get this medal or not. Use a very tiny amount of turbo before the heavy turn then when you are turning and your speed is about to drop below 800 use your big turbo on the big bend. If you time it right and angle yourself perfectly it is possible you can do it without losing any bonus time. You can afford to lose some time here if you have done the rest of the course perfect.
And presto you should have your well deserved Platinum Medal without too much struggle. It will take some practice to get this right but once you learn the track, you really should be fine.
Good luck everyone!
Here is a video below to show the demonstration of how to achieve this. I managed to get the perfect score of -0:08"001 which puts me currently 1st on the Xbox One leaderboards for this track. There is room for error and only the final big corner is the real tricky part of this track but use your big turbo at the right time and you should nail this. (Lap 3 was the lap I succeeded this time on.)