I know it has been brought up on here how changing trebles on certain fine tuned surface lures can unbalance them. Yet if this is not an issue, what is preferred? When fish swallow both trebles it can be an absolute nightmare, and chance of releasing in good health can be slim. I'm yet to find a good lure bag that doesn't play havoc in getting lures in and out of with trebles. Is it a matter of more success in the hook up rate?

And, is it true charter operators that fish out around white have a collective agreement to not allow trebles on their boats? I think I remember reading that somewhere.

For large poppers (140 g plus), a single 10/0 of the back with a baker rig double 8.0 or 9.0 in the middle is my preferred set up.  

A number of very skilled Aussie GT poppers, like rigging an assist corded single hook off the front of a popper.  I have never used this in anger, but a few cast tests tell me it can interfere badly with the swimming pattern of the lure. You need to chose your lure carefully and test beforehand. Stickbaits seem to especially effected by this method and lose their natural swimming pattern.

There is lots of debate about which size singles should be used and the main popper manufacturers are not helpful with guidance, still believing that their poppers should be rigged with trebles. Owner jobu singles are popular (but down the size by 1 as these are unnaturally large, bulky hooks). As a general rule of thumb, for a more "normally" sized hook like a Mustad Hoodlum, try a single 10/0 off the back and two x 9/0 or two x  8/0 for the Baker rig in the middle. The best advice is probably to experiment to see which single hook sizes work best on each popper.

I was initially sceptical about dumping trebles on poppers, but it is the way to go. Way better hook ups with singles and no distressing gut rips from the trailing treble. The redoubtable Nomad Sport Fishing have a good video on their site explaining all this.

Since switching to single hooks on poppers, I lose less GTs and they are way easier to de-hook and release.