Ah, good to see progress on this one. The qHack is a nice layout and a cute name!
7bit wrote:
My first question:
Is it OK to place the controller in the 2nd row from top?
Yes. It just makes the keyboard case thicker. This isn't great, but we have CNC capability now thanks to Matteo, so perhaps our cases can become smarter with a sculpted recess etc.
Do not worry about lining up the Teensy's socket to the outside. Much better we run our own internal cables instead. At least that's how I like to do it.
7bit wrote: I want to place stabiliser mounts for a 2 units BACK SPACE key where the controller is now at the HyperMicro, so there would be too many holes. I don't want to place it further inwards. It is more convenient to have it one row down.
I guess that's a reasonable compromise. A 2u Backspace seems like a waste on such a small keyboard, but they are more available than HHKB style keys.
But then again, your row 0 is crazy for trying to match to common keysets. Who actually prefers 2u row 1 Backspace to 1.5u row 2 when they have the choice? And are they likely to get a qHack?
7bit wrote: BTW: I will start with the Cherry version and make the Alps version later. It is possible to have both on one PCB, but things get impossible with multiple mount options.
ALPS: Which stabilisers to be used with Alps switches?
SP makes Alps mount MX stabs hybrid caps, right? That's your answer there. Because classic Alps caps won't work on this board. I can't even find a good Poker / HHKB style 60% block in classic Alps.
I asked Matias recently, and says he'll sell Alps mount caps (and he has some unspecified solution for stabs, too). But the best bet for a layout like this is a custom order at SP, I bet.
7bit wrote: Are Cherry PCB or plate mountable stabilisers possible?
At least I've read something like that.

Cherry stabs come in both PCB and plate mount, as you know of course, and both would be compatible with hybrid Alps centre mount + MX stab mount SP caps. So I wouldn't worry much.
Matias and MX need different plates anyway, if you want a plate in this keyboard.