I too, feel the 2018 TRS 300rr is geared too high. I looked at it from a mathematical, stand point.
40/10 is 4.0
40/9 is 4.4
48/10 is 4.8
48/9 is 5.3
I was running a 40/9...still a little fast...too much clutch action to slow it down...imo
I just installed a 48/10 on the bike, along with a new chain.
I will report back, after more ride time.