from my experiance with my pt cruiser vert i declared every single mod from wheels to custom trimmed interior to front and rear body kit,custom built twin catback exhaust, when i had a claim (somebody rearended me) i didnt have any probs as all mods were listed so i would say be honest and declare all mods for peace of mind...i was with adrian flux and they specialise in modified vehicles so understand about the custom car market....just my opinion...chris