I am currently helping my friend train a 4y.o. pony, she is maybe 12.2 HH, but quite tiny. I am around 58kg / 9 stones and 5 ft 4, so i am little worried if I can ride her. I mostly do groundwork with her and once a week I sit on her for like 10-15 minutes. I don't feel like she's having problems carrying me, so do you think she will do ok on longer rides or am I too heavy for her?