If you can do it, why not?
Teresa's top (5th) is 3000 at 75km/h (46.6mph) anyway - right in the middle between your current and to-be-modded gearing. Can't do 30mph at all in 5th, though: you have to be very careful even for 40. This is the specialty of this particular engine, you need at least 2500rpm everywhere over 1st/2nd. Yes, even for cruising.
It's said that the new revision of this single in the 2012 G650GS doesn't make strange noises when used at lower revs.