My only experience with fitting over size tyres is on my old Blade. I was given a slightly used 190 rear, the Blade took a 180. The bigger tyre did slow the handling down a small amount and one soon adapts but I would not do it by choice and going up two sizes would probably be an even bigger difference and slow things down even more.
The insurance question is also relevant too.
If you are after a high mileage tyre, many recommend Avon 3d XM, they are around £140 a pair if you shop around. I have them on my V1k and they have been great so far with plenty of grip and are wearing very well too.
My old Blade does need a set of new boots....pm sent
RD250, XJ600, VFR750, CBR900, Honet 600, RD400, RD350 YPVS, CBR600 Sport, DRZ400, XT660R, BMW R1100RS, Versys 650, CBR1000RR, Versys 650, AdvVersys 650, CB1300S, VF1000, MkII V1k, XT1200ZE