I have made a leotard in Lycra for my 14 year old daughter from a mixture of patterns that I combined (she wanted the low back from one pattern, the v-neck from another, the gauntlet sleeves from another and the bra shelf from another!) It has a very low back but it is gaping and I don’t know why? Also when she raises her arms they don’t seem to fit snugly in her armpits.  It has facing around the opening which I pulled very tight and I am wondering whether this could be the problem for the gaping back? I am going to start again but would like to know where I went wrong before I start. Are there any experienced sewers out there who could help me out? I’ve got a serger and a regular sewing machine if that is relevant! I’ve got a photo but don’t seem able to upload it…