not necessarynot necessary (unless you dont have '8 - ad recovery' in your current magldr menu)
correct. you can either use the nand toolkit, and on the list of sizes choose custom, then when it asks type 170, ,
or you could use the 180, since that will allow extra space to allow for any bad blocks, or you can look for the file flash.cfg (not flash.cfg.txt, , make sure your windows settings are showing file extensions,,,, if you see 'flash' and 'flash.cfg', , then that is actually flash.cfg and flash.cfg.txt), , open flash.cfg in notepad, look for the system line, and change the value accordingly.