I will probably get the S1 upgrade kit instead

Let's guess the HR of overclocked S3, 520GH/s for me

My guess is 575GH/s
..."BM1382 has achieved 15.75 Gh/s in hash performance, consuming less than 9.33 W on chip level at 0.75V"...
Let's do some math...:
9.33W / 0.75V = 12.44Amps ...per chip...
16 chips per blade * 12.5Amps = 200Amps per blade ...
NEEDS hell-of -a-POWER Section on the blades...

I do NOT expect that BitMain will design S3 Power section with a lot of reserves...if any...
IMHO overclocking S3 will be a challenge...if possible at all...1-2-3% max...
Not even taking PSU in consideration...
ZiG
S3 won't be hard underclocked/undervolted like S2, imho it has a lot of hidden potential in overclock that will be discovered by users. (Since bitmain has a large farm of miners is more interested to maximize energy efficiency, at the expense of a minor hashrate).