Veloc,
If you think about it logically, a 2pot design has two 'pots' pushing down on the brake pads that clamp onto the rotor. If your original design was a single pot then the master cylinder would only be made to give out x amount of pressure to work with the single pot. Using the same pressure on a 2pot effectively means more pedal travel just to push down on the pots.
In the case of drum vs disc, I've done the same thing for my own Wira. At first I thought about changing the master cylinder and the distribution valve since the rear drum would probably have less pressure than the front, but after swapping out the drums to discs, it works just as well. So I'm not going to touch the distribution valve but may consider upgrading to a Evo servo just so I get less brake travel.
Handbrake grip is caused by poor matching of the handbrake cable. You need to get the right length to ensure it grips on the calipers properly
