Brake pipe routing with manual bias valve

[RetroPug]

I wouldn't personally separate your brake circuits to be front and rear.

if one circuit fails you could loose both front brakes and have to rely just on the rears in an emergency situation.

I'd keep it as it is, even if it means having to fit two comps to the rear.

Any reason for fitting a manual adjuster?

If you brake forcefully with just the rear brakes it's not just that you'll be relying on tiny brakes to stop, you'll spin the car.