I also used USAA and had a garage fire that destroyed everything in 2016. I was dramatically underinsured so thankfully I didn’t lose the whole house (thank you firemen!!!). Ironically I had three BVM F-4s, a turbinized BVM F-16 (old school) and an Ultra Flash. The F-4s were easy...I just showed the kit cost and multiplied by three. Radio, was easy...online stuff.
Because of the size of the claim they overnighted an adjuster out who spent a week just working my claim. She was great and worked hard with me until we got to my insurance cap. Things like tools are devalued over time, so we had to get to about 50% over the insured amount before they hit the payout cap...once there any further documentation was not needed as we were at the cap
I always tell insurance companies when quoting that I want that I have stupid expensive toy airplanes and then documentation so they know what they’re getting in to ahead of time
One of the most important things USAA needed was pics of my stuff in my space/hero shots etc to prove I had it. Two of the three phantoms were just airframes and were at the epicenter of the fire. I was standing in knee deep insulation (From the ceiling/room above the garage) right where two Phantoms had been and all I could find were sheets and sheets of carbon cloth. Thank God I had taken a pic (they had only been in the garage three days) to send to a buddy, and that sufficed
Hope this helps
Dave