Hi Kyla
Yoga works holistically. Although many people start hot yoga because they want to trim, slim or build muscles (etc) and the effect is there, it is a type of exercise that one enjoys because of the many mental, spiritual, emotional and physical benefits one gets.
If you are looking to elongate your midsection may I ask you if you feel it is shorter because your back is rounded or that your midsection is more collapsed than it should be?
I do have an exercise that will help lengthen muscles in the torso while creating a strong core. This is quite the opposite to doing crunches or sit ups that shorten that area.
It is called Flatten Your Tummy And Strengthen Your Back. I receive many letters that this video helps enormously.
I hope that I have helped you.
If you want poses to lengthen your body and get leaner legs, just try the whole hot yoga series. You will be pleasantly surprised when you have a regular practice
Namaste
Gabrielle 
