Hi! I'm beginning saddle work with my 3-year-old filly and trying to build her topline up. She is a bit hollow. Does anyone have any suggestions as to certain exercises that would be helpful? She is a Percheron/Arabian cross, is very healthy and is on pasture, good quality hay as desired and Nutrena Safe Choice twice daily. She is fed from the ground as I have read that this encourages good topline. Any suggestions would be appreciated. Thanks!