Adrian, your conversion will still be ok with the non turbo single pot calipers. I have run that setup prior to this one and the brakes worked very well.
You are correct about the stock hub working with our adapter sleeve as too. It is the same hub . The beauty as you mentioned is the use of the larger standard Porsche bearings.You can change the calipers later if you like and only need to centralise the caliper. The bolt holes on both calipers are the same distance apart ,so its easy to upgrade with these later brakes.
