1. Redex is pointless nowadays, petrol contains detergents
2. Slow down from 70mph to 65 that will make a difference, you only have a small engine in it and it does not have tall gearing, as its designed for town use, stop start.
I wouldn't say pointless. Every time I used it on my old bike it'd smooth out the idle nicely. Granted it had carbs and they were probably a little clogged, but still the stuff isn't pointless.