Finding neutral can be tricky with warm/hot weather and continuous riding especially when using lower viscosity oils (30w).
I use 20w-50 oil, particularly in warm weather to make shifting and finding neutral a little easier (note that some 50w oils may decrease gas mileage to a limited extent; look for Castrol 20W-50 or similar, you don't need to spend lots of $$ on specialty oils).
65-70 mph is about the top comfortable speed for me and the 450 Rebel. I much prefer 50-60 mph (less engine noise, no vibration, still has some top end left, feels more stable, etc.).
Happy riding and God bless....