[Mart]

The master cylinder is smaller than stock so will need more pedal movement to move the brake shoes out.

Personally I would fit a new single circuit master and if all the other things are as intended it should work well.

Shoe arcing is important but can be achieved with sandpaper on the bench.
Make sure you have the pushrod length right. Too long and the brakes will bind up.
Too short and you will have lost travel at the start of the pedal.

Make sure the piston is in the right position when brakes are off. Just clear of the recuperation port is ideal so the minimum travel is needed to close off the port. If the piston moves more than the minimum then you have lost travel before the brakes are applied.

Look for a small blip of fluid from the port as the pedal is applied. If the blip is more of a healthy squire then you could probably shim the piston forward with a selected thickness washer to minimise lost movement.

But personally I'd go single circuit with the correct diameter cylinder, but still shim if necessary.

The single cylinder has the residual valve built in.

Mart.