I had tried to reduce the number of force_encoding, but was unable.
Tried your solution, it works, passes all the tests

But,

MRI
```
"\u{876}".encode('utf-16be').dump.encoding # => #<Encoding:ASCII-8BIT>
```
RBX
With your fix
```
"\u{876}".encode('utf-16be').dump.encoding # => #<Encoding:US-ASCII>
```

Is this ok?