if you are motivated - anything can happen
training can overcome a lot of difficulties (size would be one factor in your case - but who knows - its not uncommon for you to grow a couple of inches in a year)
a good training plan and healthy nutritition - might want to increase the duration if 30mins is the longest you do.
try and build up that aerobic base for the upcoming rowing school.
no doubt they have good coaches there and it will be hard work...