Whirlybird
No one is speculating on a definitive cause at all
What is good about the speculation is that it is taking into account all possible scenario's which is increasing everyone's awareness of all the innumerable risks that this flight faced.
Weight
Balance
Density altitude
Performance charts based on a 'new' aircraft
fully functioning (or otherwise) engine and prop
fuel contamination
Field conditions
prevailing wind
etc etc
We are all thinking about all of these factors just that little bit more now and that is no bad thing.
Having said that, I am quite sure that on Sunday evening when we all heard the news on the radio or TV the first things that we thought were:
Cherokee 140
4 on board
channel crossing (fuel load)
hot, muggy day
And that is why so many on this forum and elsewhere will not be surprised at the outcome of any AAIB report because even if the factors are none of the above - the safety margin for error (or other failure) because of the above was NIL.