aarch64 on pi3 advice

[tech-lists]

Hello list,

I've installed aarch64/pi3 cross-compiling on an i7 via crochet onto a
pi3 machine and it seems to work well. Please advise:

0. I've fount a config.txt in /boot/efi. Where can I set the speed &
memory/GPU and what's the syntax?

1. Can I mount /usr/ports on say a usb stick, compile from there and
expect it to install OK? /usr/ports would be a symlink to
/32GB-usbkey/ports. I see that ld & ldd are present, so I guess I can
compile from ports?

2. I'd like to strip out WITNESS and friends and recompile the kernel.
Can I do this on the rpi3 and expect it to work? Should I? Or should I
just do this on the faster i7?

3. If I have to go down the route of cross-compiling another image on
the i7, is there a way I can also install a selection of ports to the
image before using the image on the pi3?

Many thanks
-- 
J.