Agreed. But i never understood why the insurance companies settle, with the policy holder, if you pay the extra because what incentive is there to declare your mods if you are given a second chance to pay IF you crash. Surely the insurance would just love to stick two fingers up at you and say "your problem"?
depends on the insurer
ultimately, the difference is all it actually cost them. You took out the insurace so they were going to have to pay anyway
the only thing they've lost out, is the extra money they would have charged you. The reason they usually only cover 3rd party losses and not your own is to deter you for this type of thing
but its entirely situational, and i expect there will be lots of variables, such as the ammount of mods not declared, the ammount of money involved for repairs etc..