Allegedly Dennis did his own mix of POB as well; if that still exists I'd love to hear it. I don't know why it wasn't slotted onto the POB reissue in the first place. I think there would have been enough for room for that without losing the outtakes.
I think "allegedly" pretty much sums up that statement. There are some tatty reference cassettes with rough mixes, mostly incomplete bits, some of those mixes were done by Dennis just so he could go home and listen to stuff...as well as some of his engineers and friends. A few of them are what i guess you'd call complete...and a few of them are revealing at some level, better even. But in no way is there a complete POB album mix done by Dennis, let alone one that exists on actual studio reels. One of the most interesting things that remain from that era are longer edits, like Rainbows exists with a bunch of extra parts. The POB rehearsal tapes have way more lead vocals on them than i had thought years ago, and apparently there are reels of Dennis/Christine recordings in existence...again more reels than originally thought...not in the possession of Guercio though. As was mentioned up the thread Guercio was toying with a plan to pull these things, a few more unreleased POB/Bambu tracks and other odds and ends together for a release titled "Tornado"...(title was my suggestion to Guercio by the way)...Dennis had used that as a working title for one of the three CBS/Caribou planned albums he signed his orig. deal to record...POB being the only one that made it to the finish line. I'd love to see Guercio do the third chapter, even if it is odds and ends because so many of them are great.
The POBN tour rehearsal tapes are up there at the top of my bucket list of recordings I want to hear before I die(as well as the four taped Beachago 1975 MSG shows, but that's another topic). PLEASE do everything in your power to get Guercio to release them!

On a slightly related note, I have always wondered if there are any recordings that exist of when Dennis did some POB songs when he was the "opening act" at a few Beach Boys shows.