I am not a racer so can't give you any advice (except maybe
do cyclocross?), but I don't think 6'10" on a mostly flat ride is good. Could be that your small size is a disadvantage on the flats, since your overall power will be lower, but it's only 10 minutes faster than my first ever (accidental*) solo century with 4200 ft elevation, 2 categorized climbs, and 30 miles on busy MUPs during a weekend in July. I spent most of the ride with my HR chilling in the middle of Z2/Z3 as a 36 year old, 135lb, 5'9" road cyclist with half a year of experience almost entirely from bike commuting. But you are young and have plenty of room to improve.
*Accidental because I was only planning on going about 97 but encountered a road barrier and got lost meandering around looking for a detour at mile 80.