Quenya sentence translation (for a tattoo)

Hello:) A friend of mine has asked me whether it would be possible to translate the following sentence into any Elven language:

"Only bent does the bow show its strength" which is my translation of the German original "Erst gebeugt zeigt der Bogen seine Kraft."

I've decided on Quenya. What I've got so far is:

Rië cúna quinga tanas tuorya (I've specifically tried not to use Neo-Elvish words.)

Since this is for a tattoo, I really want to be as accurate as possible. Could you possibly help me out on this? I'm particularly unsure about the adverb "rië", the position of "cúna", and the inflection of the verb "tana-".

I would check with the reddit Quenya group. I wish I could help but I don't know enough about Quenya to be any help.

Alright, thank you for your suggestion!