I would go with the single speed if racing. My yusa with the 2 speed gets sideways when shifting under power. Fun when playing but i can see it being a big issue when racing.
By dm-1 do you mean the 1/7th scale car or the newer, shorter one with the std rear shocks and the pushrod front shocks?
The newer shorter one. What medusa on 4s would be goog for this project ?. I cant afford another neu .