Even if you do upgrade to metal clevis you need to put a piece of fuel tubing on the clevis to keep it from opening up accidentally. But having trained more students than I care to count (and seeing many different trainers) I can tell you that the supplied plastic clevis that come with the trainer are more than adequate for this plane. Put fuel line keepers on them and you'll be fine. Upgrading to metal clevis is just spending money that you could spend elsewhere.

Hope this helps

Ken