I'm so sorry that you are going through this. Personally, I think I would cancel too if my lining were not at 7 or better. I will say that I have heard of people having success with smaller linings. In fact I used to post with a woman that had twins with a lining of six so you never know. I guess my thought is that because so much is at stake, I would want to have the optimum environment in which to put my embryos back. If you were to put them back at a less than 7 lining would you second guess your choice if your cycle was not successful? If so, I would not do it. I would also consider the FET success rates of your clinic. If they are very low, than perhaps you might do better to have a fresh transfer with a less than optimal lining. It's just so hard to know what to do sometimes. Whatever you decide, good luck.