i had DFET on thurs 2nd dec and i have not heard anything about them implanting late, i.e. i had no idea when they were 'supposed' to implant but as the doc was doing the procedure he said they would implant that day or the following day (friday).....so that's all i know about it really. Others may know more
I think that frozen embryos implant at the same time as fresh, I suppose if they had lost a few cells on deforst it might take them an extra day to catch up but I would think that would all, How old were your embies?
You have tested early though so I would hang on in there until the 9th- clinics give test dates for a reason and it is so HCG will be in high enough levels to show on a pee stick,