I haven't gone through this since there is no way I will turn off SIP (it's too important), but you should be able to figure out why the size is increasing and address it. The recovery partition should not be changing in size at all, is the OS DMG partition increasing? Are you ever booting to the OS itself, which could be creating a swapfile or something like that? Are you using the right DMG type in Disk Utility (compressed, read-only I imagine)?
Do you mean once you capture the final DMG with SIP disabled, it's twice the size of the original AutoDMG image?
Regarding documentation, I think you're going to be fairly lonely in that area unfortunately. As an MSP, we've taken the descision to not document, blog or otherwise share info regarding disabling SIP. It's just too frowned upon.
Just out of interest, what's the need for disabling SIP in your case?
I wouldn't disable it - it's important and Apple is pushing it, which means you'll be swimming upstream here. There is a rootless.conf file in /System/Library/Sandbox/rootless.conf. You could try messing with that but I feel like I'm giving a gun to a kid here. Don't shoot yourself.
SIP's active configuration is stored in NVRAM, not on disk. Trying to build an image that includes SIP being off is not going to be a successful process unless part of the process includes:
A. Booting to the Recovery environment
B. Running "csrutil disable" while booted into the Recovery environment.
This process would have to be repeated on every machine you want to disable SIP on. It will not be included with the image because the configuration SIP is referencing isn't stored in the image, it's in NVRAM.
I have several posts on SIP and how it works available from here:
https://derflounder.wordpress.com/category/system-integrity-protection/
Edit: And Rich beat me to it!
That won't disable it.
The setting is stored in NVRAM, not on disk. You can't "capture" a sip disabled OS DMG