I think we've seen enough from Son to know he's far better when occupying a wide position, rather than leading the line. He's not a lone target man and doesn't like to have his back to goal.
As for Chadli, There's no getting away from the fact that he pops up with the odd goal or assist every now and again. I just don't feel he contributes enough over 90 mins of football. If we're looking for back up for Kane, we need Chadli offering the same work rate and the ability to be a dangerous target man. Personally, I don't think he'll give us that. I can't help but feel that despite Chadli's size and physique, he'll be more concerned about ruining his pristine hair.

I guess we'll have to trust Poch on that one, he sees him train every day. The worst thing we could have seen today was Chadli getting 2 goals and an assist, 2 days before deadline day!!!
The news today is that Dembele is having a medical, (so he's pretty much signed). But I wouldn't be surprised if the exact details of the deal are kept quiet, in terms of whether he's going back on loan or not, in order to help our bargaining position on deadline day with other clubs.
The guy is 19, so loaning him back isn't actually a bad idea at all. It didn't do Dele Alli any harm! The difference being that no one really cared with Alli, because we had so many midfielders. Not the case this time!!!
Even with Levy's track record, I'll be amazed if sufficient back up for Kane isn't taken care of.