KF8 Personal Documents display as older mobi 7 docs

I've noticed that Personal Documents formatted for both mobi 7 and KF8 that are compiled (without error) using KindleViewer 2.4 do not display as KF8 on the Fire, Kindle for Android, or Kindle for iOS when they are sent via the Amazon cloud to those devices/apps. However they do display as KF8 when sideloaded. I've sent an inquiry to Amazon concerning this via the support channels through my Kindle Direct Publishing account, see below for copy of my inquiry. I'll post their reply when/if I get it.

I have created a book I plan to publish soon. I created my book using HTML5 and CSS3. I used the @media statement within the CSS to differentiate between mobi 7 formatting and KF8 formatting. I also created the appropriate content.opf and toc.ncx files. Using KindlePreviewer 2.4 the files compile without error. The resulting book file looks great on my PC. It also looks great on my Kindle3 Keyboard and Kindle4 non-touch when sideloaded to them. The mobi 7 formatting works well. It also looks great on my Kindle Fire and in the Kindle for Android app on my Android phone when sideloaded to them. When sideloaded the KF8 formatting is displayed. I then emailed the file to my Amazon cloud to become a Personal Document. When I send this Personal Document to my Kindle Fire, Kindle for Android app on my Android phone, and Kindle for iOS app on my iPod touch, the KF8 formatting fails to display. Instead I get the older style mobi 7 formatting. The Fire is running firmware 6.3 and the apps on my Android phone and iPod touch are the latest versions. Will Personal Documents not display as KF8? Or is this a bug? If Personal Documents cannot be displayed as KF8, then how can I test books on my iOS devices as I cannot sideload to them. It is very important for me to test books on all devices before publishing.

[tomsem]

Yes, they have yet to add KF8 support to Personal Documents service. They strip out the KF8 segment. I keep checking, and sending nice messages to kindle-feedback, and hoping that will change.

You can upload to Dropbox and then download to Fire (or K4Android?) if you install Dropbox on the same device. Then use a file manager to move it to the Documents folder. It seems I have to restart Fire before they show up (firmware 6.3). If you have the email client configured, sending as a file attachment to that address might also work, but I haven't tried that.

After a long delay, here is the worthless email response I got back from Amazon CS:

I'm sorry for the delay in responding to your e-mail.

Personal documents do not support KF8. Only KDP supports KF8.

I would suggest you to upload the KF8 file via KDP, download the MOBI file and view it in Kindle Fire.

Follow the steps below to open the file using Download book preview file option:

1). Visit https://kdp.amazon.com and log in.
2. Check the box at the left side of the book and then click on the "Actions" button at the top left, then choose "Edit book details."
2). Scroll down to the bottom and click "Download Book Preview File"
3). Click on "Save file" and "Ok"
4). Give the file name as "content123.mobi" and click "Save"
5). Now open this file in Kindle Fire to check the formatting.

This of course does no good for Personal documents.