To work out the overlap, all you need is the duration and centerline of the lobes and an understanding of cam dynamics.
For the intake low speed lobes I would make the lift of the lower lobe the same as the higher lobe and increase both by a small amount aiming for a lift (at the cam) of 9.8mm . I would set the centerline of both low speed lobes to 108 and increase the duration to 240 degrees. If you go higher than this, a hole in the torque curve will appear around 3000rpm so you will lose power by going bigger. Sometimes less is more.
For the high speed cam, I would leave the duration and centerline alone but lobe height needs to be increased to keep it 0.14mm less than the low speed lobes new height. This is for mechanical reasons. The valvetrain configuration is intolerant to arbitrary cam specs as everything must work together to enable the lobe switch.
The exhaust lobes are pretty good on duration, lift and centerline already. I would be reluctant to alter too much here. Maybe just increase the lift a fraction.
If you want a preview of what it would be like to have much bigger low speed cam lobes, apply a constant 12V source to the oil solenoid that activates the high speed cam and take it for a drive.....