I'm 4dp5dt. I thought I had line eye last night and this morning (going to double check this mornings but I already chucked last night's). I couldn't see it very well except for photographing it. Last time I had a clear positive on 6dp5dt with a 6AA (already hatched). I know EmLou didn't get hers until 9dp3dt and then it was barely darker than mine is.
Unless you like obsessing and are a POAS addict (with enough $ to fund your addiction) then I'd wait until 6dp5dt - that's when they say you should get an accurate result.