My first pony was a sec c, she was wonderful (despite decking me a few times!). I rode her until I was about 16 - so about 5'4'' (lanky legs) and 8 stone. I stopped riding her due to her retiring rather than a weight or height issue.
I had a grey 13hh welsh C. He was the most loving, friendly pony you could ever meet. He used to whinny so loudly when he first saw you, then whicker until you got up to him and then wait for a cuddle. He wasn't the bravest, but was the so friendly.
I had him as a child (sold last year) so at my biggest I would of been 5'4 and probs around 7-7 1/2 stonne. ( not anymore though )