I've asked, I've tested - no big deal 
I've just bought this router so I could test images, even faulty.
Netgear has a nice bootloader with tftp, so easy to revert faulty image, even for noobs.
Yup. The easy recovery from brick is feature that many overlook when selecting a router. The TFTP in R7800 is super-easy (as it is also in my WNDR3700/3800 routers).
I have used R7800's TFTP recovery today 5 times, as I have tried to get a kernel 4.9 based firmware running, but so far no success...
Well, my priority was powerful hardware and LEDE support. The old TP-Link 3600 got hiccup and been overloaded with OpenVPN, 1-wire, Postgress, several WiFi clients and dnsmasq hostfile with nearly 0.5 million blocked sites 
Now R7800 is boring although OVPN uses AES256 instead BC and Adblock shows nearly 1mln blocked domains...
Oh, and I hate extroot
Thanks to cezary for the build!. Runs nice and smooth with all the flash memory available. Also thanks to Wally and hnyman for the tips in this thread.
I tried sysupgrading from Cezary's build (used it to get more space) to hnymans build, it leaves the router in an unsuable state and I end up tftp installing stock. I unchecked the keep settings option while upgrading, I wonder why I cant upgrade to hnyman's build.
'Coz has different flash map. If You want to flash image with different map/OFW You have to always flash 'factory' via tftp - 'sysupgrade' image doesn't change partition map. Check my translated tutorial (link is a few posts up) - I've tested migration in both ways (sysupgrade too).
Ok sorry, I misunderstood earlier (I mis read the information in the link you posted) for some reason I thought you could upgrade after the partition changes, my stupidity lol. Anyway thanks for clearing that up.
Netgear partition might have the Genie and other readyshare vault store in it might be .
There are also additional languages and saved settings (in OFW) as I could seen in hexeditor. So I've suggested backup all partitions before changing flash layout, just in case.
Anyone have actual partition layout.
Not exactly 
Many users looking on flash capacity when searching new router (as me) to avoid extroot. So if You get 19 instead 100MB, there is something that makes You searching deeper. Believe me, there are many users that use firmware with expanded flash not default in LEDE, especially on Netgears. The only way is custom build. So, make backup and free Your router
So even if the 128MB flash available to one. Is there any firmware that can take advanatage. Like say PFSENSE is almost an OS. A mini version of it.
LEDE? It's a comlete system with bunch of packages. You can do what You want - it's clean Linux. If there's something missing, You could write Your own program/package/script. It's flexible and open. And that's why You need as much flash as possible to avoid extroot.
If You use minimal image even 8MB flash will be enough, but try to use more services, install packages and popular 16MB is not enough.
As routers're going more and more powerful why should we be limited to basic services? Todays routers are like servers in not-so-far past: compare R7800 to i.e. basic Sun SparcStation II
I made the DTS changes as mentioned in the second post and compiled using hnymans build environment and its working for me now.
So cezary when is the next snapshot build due?. Are there some interesting changes?
Best!
@avx seing that it worked for you, i've done the same and yep it works nicely. I've also restored the mtdblock backups @Wally recommended doing prior modifying the DTS to see if i could go back to OEM firmware and it also works.
I find @hnyman's build very interesting, and i think i'll stick with this one.
Wally mentions writing the partitions back from backup to return to stock but I found a simple tftp flash to stock got me back and my settings are automatically restored, so no need to setup up again in stock firmware. But yeah, still best to keep a backup of the partitions in case something goes wrong or gets corrupted.
TFTP always work - this is the beauty of R7800 
You can't softbrick it. You can flash OFW without restoring backup, it will work but some things could be missed, I didn't tested everything but looking at partiton dump I saw some strings related to languages, settings etc. I suggest restore to get state as before modification. Just in case.
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You could restore back to ofw because even you remapped partitions, data there has not been overwritten yet. If you fill up your nand flash then you may have troubles coming back.
True, thanks for the replies guys. Still learning, I'm still a noob 
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