I got a new bike for Christmas but the saddle was too low when I got it (I didn't get a fitting when I brought the bike - but it is the right size). The saddle is still too low and I keep putting it up by half an inch at the end of every ride. I don't know what the required height is for the saddle (i.e. how will I know when it is too high?) It is a Trek Navigator T10 (a hybrid).