ND2 RF Seat Lowering kit

Just wondered if anyone here had any experience of buying and fitting a seat lowering kit for an ND2 RF, and if so if they could advise on a few things?

1. How much does it lower the seat by approx?
2. Which is the best kit and where to buy?
3. Is it easy to fit DIY or is it a specialist/garage job?
4. Does it count as a modification for insurance purposes? Does it affect or compromise seat security/safety in any way?
5. Having done it, are you happy with the outcome etc?
6. Did it require any special tools?
7. Does everything fit straight out the box or did you have to mess around altering or changing things or does everything ‘line up’ etc?

Thanks in advance; any help much appreciated.