Indeed, holding 51% of a crypto coin in a single wallet/address can lead to a double spending security risk for that block chain. I sincerely recommend against holding more than 51% of any crypto coin or coin age, including that of TrustPlus.
I don't know if/why holding 51% or more of TrustPlus coins/coin age would have been recommended to anyone. I hope that TrustPlus will be allowed to develop based on its own merits if/as folks contribute code to this open source effort, as it is meant to be.
As I stated earlier, if blockstream's sidechains efforts are successful, I will be making an attempt and effort to incorporate that technology into TrustPlus as another open source contribution.
You can learn more about blockstream's side chains at
https://blockstream.com