Yes I've tried Yau in the past but what works well for others doesn't seem to work well for me here.
I was amused in a recent competition to overhear Rob Yau himself being asked if he used the Yau Method.
Sub-3m is definitely doable. My records show that my first sub-3m single came on my 555th timed solve and my first sub-3m Ao5 came from solves #1002-1006, but you're so much of a better cuber overall than I am that I'm sure you'll be there in a fraction of the time it took me.
I had to settle for my 2nd-best 7x7 solve on Christmas morning.
Awesome. I was also a good boy this year and Santa brought me a copy of Cracking the Cube too. Looking forward to getting stuck into it, although several other reading-related presents will be competing for my attention.
Other than the first solve, Square-1 didn't take me too long to figure out. This said, I haven't been practicing it recently and the algs I did know are likely fading from memory. I was never fast at it anyway. From memory, my PB single was 1m 57s or something similarly useless. I do like the puzzle though and will return to it later in the year. No SQ1 at the Birmingham Open (not that I can definitely make it there for it) so no immediate focus needed on this by me.
Is your sub-15 target for Clock at home or in-comp? Hope you enjoy Clock; I think it's an under-appreciated puzzle. Good to have 3 delegates in the UK who are all fond of it.