I have just been fitting my bias box to my little austin I am building as a daily, Discs on the front, calipers using no more volume than a Lockheed M16 rears are stock anglia drums, so, in reality the braking system uses no more fluid capacity than a Mk1 Mexico, or similar.
My bias box uses 0.70 and 0.626 cylinders, my logic says put the smaller cylinder to use with the front brakes and the larger to the rear, then adjust the bias to get a decent feel, I know using the smaller cylinder this way will give me a longer pedal but better feel, reading else where there seems to be a bit of a split of thoughts in which way to plumb the system and what cylinder sizes to use..... thoughts anybody?

There is not enough information in your description as the ratios are dependent on more than the volume of fluid and diameter of the MC.

For a braking system the main variables are:

1. caliper piston diameter
2. number of pistons in each caliper
3. disc diameter
4. pedal ratios
5. drum diameter
6. drum brake cylinder diameter.

Realistically its more trial and error, the diameters you have chosen will be a reasonable starting point.

Additionally adjusting the bias on a bias bar will not change the feel it will only change the front to rear balance, feel is just down to the combination of all the other factors.