There's no need to tell them about shocks or fork upgrades, you can't ride the bike without either of them they aren't additions. They don't enhance performance, albeit, you be able to ride slightly faster over any given stretch of road, but power isn't increased.
Even additions that don't enhance power like legle end cans (providing they cost no more the a standard system) most companies aren't interested. Things like screens, heated grips, tail tidy, luggage systems, rearsets, air filter changes, huggers, steering damper, crash bungs/bars, brake hoses.
This is the current list of things you don't need to tell Bennetts about:
• air filter changes
• bar ends
• braided hoses
• decals/stickers (unless race replica)
• disability adapted
• exhaust (road legal)
• grippers
• heated grips
• huggers
• lights/indicators/mirrors
• scott oilers
• screen changes
• seat cowl/single seat units
• seat replacement/changes
• sissy bars (long backrest)
• tail tidy
• tank pads.
Everything else (except 'consumable' parts like tyres, chain and sprockets (as long as the gear ratios remain the same), bulbs, etc.), you have to tell them about, and the following modifications are specifically listed on my policy now:
- fairings added (inc belly pans)
- Crash protection (bungs and bars)
- Rear shocks / front forks (up to £1000)