Phoenix isn't too crazy.

Just send yourself the absolute maximum you would ever keep in that wallet. It's self-custody Lightning, so maybe a few million sats tops, right?

This will result in Phoenix adding some of their own liquidity to that amount when they open your channel, so you will have a channel that is larger than you would ever really need.

Now send most of those funds back to yourself on-chain using Boltz.exchange so you have a more reasonable amount left in Phoenix.

Now you will be all set for transacting with low fees, and no surprise larger fees for running out of incoming liquidity.