This is a weird case to me, I have no problem holding an advance frog stand and frog stand longer than a min. I think I have enough straight and bent arm strength and also balance for my elbow lever. However, I can only do my elbow lever when Im wearing a shirt or when im a bit sweaty, when im not my elbows just slip off. At first I thought its becuz of my form, so I hunched my upper back harder, tight core and maintain my hollow body better. I also stretch daily in order to improve my shoulder and overall flexibility. Still it slips off, need help.