Is it (cutting down the front sight) a good idea ?
Not really............. Think about it a little.
The pics you've seen, known as a 6-o'clock hold, are for target pistols, which have their adjustable sights zeroed to impact the bullets a few inches high at that known target distance, so the shooter can hold as you want to (for a clear view of the bulls-eye), yet have the bullets hit the center of the target above.
Your SP-101 is a fixed sight self-defense gun - Which type guns are usually preferred to shoot POI right at the POA, just like your gun currently does (Perfect).
If you think about it, when practicing, it doesn't really matter if your bullets impact the center of the bulls-eye - IMHO, it's much more important they impact right where you're aiming.
SOOooooo, if you get consistant shooting, right where you're aiming (at the bottom of the black bulls-eye), I would say you're good to go.
Unless you're into an ego trip, of course - and just HAVE TO impact the x-ring.