@omer : my replies are inline. hope it helps...
Santro/Cultus have a dual pin coils for each pair of cylinder, (you will be using only one node of ignition coil in paiggo as it has only one cylinder) I bought it 4year ago for 400RS only it has a bigger longer reliable spark I tested it along genuine ignition coil which had very smaller spark.
How it helps : Bigger flame more combustion, complete fuel burns = More Power (actually complete usage of Bikes Power Band and better mileage)
Yes its small enough to fit exactly where the original one is fitted, and it has nothing to do with increase fuel consumption, all it does is to burn all the fuel came from inlet valve to chamber to increase performance, use STP Octane booster to further enhance the performance and redline line paiggo to 11000+RPM ... you will be amzed with the performance with Octane booster because paiggo has a higher compression engine relative to other bikes in market.
Yes the orignal magnetto is a 3-Phase Generator with enough grin dont worry. 
Only do it if you are planning racing and high speed cruising, but if you are a laid back rider then why bother ? bike is working already anyways ?
only higher conductivity Plug cable+Coil and you can install it your self not a rocket science, or cal get help of any bike electrician, or better would be to try running bike richer on fuel and put octanne booster and cruise it on 5th gear to see if it completly redlines or not, if it doesnt then get the compression checked first may be rings are weaker, or any valve is leaking pressur if both are correct then you have a lousy spark the go for a pulg change along with coil and wire.
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happy Riding.