I will describe my flowless downgrade that I did yesterday, to help someone.
Note that I used the Tuxhs version of sysUpdater.
1- Did a System Format, got a fresh 10.3.0-28 O3DSXL;
2- Formatted the SD card and put the homebrew startkit;
3- Powered on, system created file database for titles;
4- Switched theme to colored one, than back to default;
5- Used browserhax to launch Homebrew Launcher;
6- Installed homemenuhax, with control trigger type1 (will ONLY boots in homebrew if I did press a combination of buttons of my choice);
7- Powered off at Homebrew Launcher;
8- Powered on to see if menuhax did not trigger by itself, and went to Home Menu, as expected;
9- Powered on holding my triggers keys, booted to Homebrew Laucher, as expected;
10- Powered off, removed SD Card;
11- Added the sysupdated app to '3ds' folder;
12- Unzipped the 9.2 (Full) for OLD 3DS US (CHECK 4, 5, 10 TIMES TO SEE YOU ARE USING THE CORRECT PACK FOR YOU DEVICE!!!!!);
13- copied the 'updates' folder to SD card root;
14- did a md5 check of the 'updates' folder, to ensure no error occured while copying;
15- OK, all ready to go!!!!
16- Powered on holding my triggers key, Homebrew Launcher, and attached the power supply to ensure it's charging;
17- Opened FtBrunny app and exited by pressing L+R+Down+B;
18- Opened SysUpdater;
19- All steps went ok, success to get all services granted;
20- Waited about 10 seconds to pray;
21- Pressed the Y button;
22- Waited for the 'Getting CIA information' mark, about 15 seconds;
23- The system started install every CIA;
24- About 5 minutes later... Finishe with message 'System will reboot in 10 seconds';
25- Waited more than 30 seconds, and realized the app did crash (was a common behaviour of memchunkhax at the moment);
26- Did a manual power off by holding button;
27- Powered on (without pressing any button;
28- System was downgraded.
Hope this steps help. I did tried 1 time ever, was very straightforward.
Also, I did tested many build of memchunkhax2 earlier, and got the 0xDEADCAFE 100% of time.