6.x jailbreak

so, I finally took my old fat PS4 out of storage, and it's on 6.51 firmare.

Before I start working on PS4 homebrews, I need to jailbreak it, so... a simple question:
What's the recommended firmware version and jailbreak to use in this case?

I assume I need to upgrade to 6.72 and then use the 6.72 hack, but if there's any special hack for 6.51 then I can try it too.

I know that success rate ain't perfect with these jailbreaks, but still, if I want to develop for the PS4, this is something...

6.x jailbreak