Butt splice connector to join 10 gauge to 12 gauge wire?

I don't trust wire nuts to hold. This is especially true when joining multistrand to single strand, but can occur for any type of wire connection. I always use electricians tape to be sure the nut holds both initially and will continue to hold with years of vibration in an RV. Of course this looks like cr+p and is still not dirt or waterproof. There are several styles of more modern connectors that work better, last longer, are waterproof if needed and look more professional.